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ORNL-4762
UC-70 — Waste Disposal and Processing

 

CONSIDERATIONS IN THE LONG-TERM
MANAGEMENT OF HIGH-LEVEL
RADIOACTIVE WASTES

Ferruccio Gera
D. G. Jacobs

 

 

OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION
for the

U.S. ATOMIC ENERGY COMMISSION
ORNL-4762

.Contract No. W-74L05-eng-26

HEALTH PHYSICS DIVISION

CONSIDERATIONS IN THE LONG-TERM MANAGEMENT
OF HIGH-LEVEL RADIOACTIVE WASTES

Ferruccio Gera and D. G. Jacobs

FEBRUARY 1972

OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37830
operated by
UNION CARBIDE CORPORATION

e T

3 445k 0023182 &
CONTENTS

ADStract vttt it i i i i i s st s i e e
IntrodUCTion v eieeinnieneeesesnoaseasessancsocsonsonss .
Projected Waste Problem ....v.ivsveeennvensnaseoconossas cen
2.1 Potential Hazard Index .......... c et e i e e e e
2.2 Potential Hazard from Plutonium Isotopes ..............
2.5 Comparison of Inhalation and Ingestion Hazards ......
2.4 Steps in High-Level Waste Management ........eoe... coes
2.5 Evaluation of Risks Associated with Waste Management ..
2.6 Advantages‘of Disposal in Salt Formations .....ceeovue.
2.7 Retrievability of Stored Wastes .........cvveunnn voee
2.8 References .uv.eeeeeecesnennns e es et con
Characteristics of Solidified High-Level Wastes ........ oo
5.1 Leachability covieeieerioeeeaesoeseserssosonsosoanansns
5.2 Heat Generation Rate ....eiie ittt neennanonns
9.9 RETEreNCES titeeceeeesesesossecossosossossascsosesosssassosssss
Interim Storage of Solid Waste ...iv it nnorenronerennanns .
4.1 Routine Operation of Interim Storage Facility ...... .o
.2 Siting Considerations ..iveieeeseseeesanssennonnnas cene
4.3 Possible Mechanisms of Activity Release During Interim
SLOragE tovreeenersennoeonsassnesones ceecanae ce e
h.L  Movement of Radionuclides Through the Ground ..........
.S CONCLUSIONS vttt e tonereneeeeaenoenseesoesenoeaasnnans
o6 REFEIEIICES 4evreersonoonssseessoansssssaanoosssesnnnases
Geologic Processes Relevant to the Ultimate Disposal .......
5.1 Stream ErosSion c.oeeeeeieireeieesesoseeetssosesssencosasss
5.2 Orogenic and Epeirogenic Uplift .........civieiieenn,
5.3 (Glacial EroSion «eeeeeeeeasoecesosessassssosssesonsoasse
5.3.1 Cause of Glaciation ...ceveioiesecescssoconnnnss
5.3%.2 Uplift of Previously Glaciated Areas ...........
5.4 SUDSIAENCE ver ittt ittt C et et
e VOlCANiSM teseeesooessoeasasoosssosssssossssossssosssssases
5¢6 Faultifg veeeeeneeoeosessaanasss et eees et ceeeea
5.7 HyQroOlogy ceeeeeseeeenetsoesesocaosssaoossossaoscnssasss

iii

38
45
51
56

60
69
71
7h
75
76
79
79
80
CONTENTS (contad)

5.8 ConcluSions v.veveeeeeeeeeneens C et ettt e e
5.9 RelerencCes tuieeeesesesseseenesssssonossosssssssssosssoassas
5.10 Bibliography +oeeeeeesisneestessessossasessassnsonssnss
Possible Release Mechanisms After Disposal in the Geologic
FOormation .s.eeeeeeieeeenenseenonsenns C et e e et e
6.1 Catastrophic Bvents ........eviiiiiiiuiiiiiiiiiiiiinn..
6.1.1 Meteoritic IMPACE vuuerereresnerenneennsonnennnns
6.1.2 Volcanic ACTiVIEY wewerrrrreeereeeeeeenonnennnnns
6.2 S1oW Ge0logic ProCESSES it vrereererersennonnnnnnnnenas
6.2.1 FaUlbing ceveeeeeenenennnnnneeeneoeeeeneaennnnnns
6.2.2 Erosion seeeeeeeeerianenann e ee e,
6.2.3 Leaching and Transport by Groundwater ...........
6.3 Plastic Deformation of the Disposal Formation ..........
6.3.1 Salt Diapirism ..evevveeennnnn.. e ceees
6.3.2 Shale DiapirishM .vuveeeerrennennnn et e e et s st
6.4 ConcluSions eeeeeereeenereeenan et eeee e et
DD RO O O ICEE ettt sosunessonsesseessassoseesssessnneneas
Summary and ConcCluSionsS t.eeiieertoseenaseessosassensnnnssoses

Appendix A--Estimates of Radionuclide Movement Through the
GIrOUL G v e v ensosseeessossasosesosssassssscsssosassssosesonsses

Appendix A--References ...ceeeievnoesencens f et e e

iv
LIST OF TABLES

Estimated Wastes from Light Water Reactors in the USA..

Estimated Wastes from Liquid Metal Fast Breeder Reac-
tors 1n the USA ..ttt eersnnnnns ceeeesaennas oo

Amounts of Some Transuranium Isotopes in Light Water
Reactor Fuel ...iiiiiiiiiieiniesaseesnssnsscsnsassnas

Amounts of Some Transuranium Isotopes in Liguid Metal
FFast Breeder Reactor Fuel ......ciiiiiii ittt innenns

Potential Hazard Index of Several Significant Radionu-
clides Accumulated in High-Level Solid Waste by the
Year 2020 v eeuieereeoeseseeosossnsssssssossesssonsoennas

Fifty-Year Dose Commitments Resulting from the Inhala-
tion of 1 uCi of @IIPUO, verrrrnrervnnnnn.. e,

Characteristics of Solidified High-Level Waste ........

Range of Chemical Compositions of High-Level Liquid
Waste coeeennnns .

Chemical Composition of Major Materials from Nuclear
B IS d0n v ittt st i ineeeneotessoeseseeeoesacoocsacenenees

Heat Generation Rate in the Waste from the Reprocessing
of 1 Ton of LWR Spent Fuel .....iiiii e irnnnnns

Heat Generation Rate in the Waste from the Reprocessing
of 1 Ton of LMFBR Spent Fuel ....uiiiiiiiiinienrnnenssss

Heat Generation Rates in Solid Waste ..oe.ve e reneeenns

Thermal Conditions of Cylinders Full of Waste with the
Highest Heat Generation Rate ...t iieninennonnnns

Total Heat Generation Rate and Thermal Flux in Freshly
Filled CylindersS veeeeeeseeeeenosoeesoesssssssssenscoens

Inventory of Volatile Radionuclides in Freshly Filled
CyLlindersS ot eieneeeeessssoeseseoassssssssessesssssans

Past and Present Rates of Denudation ....veievevinenn..n.
Rates of Regional Erosion in the United States ........

Rates of Erosion Based on Data from Archeological Sites
NEeQy ROME 4 ewesesescesessesssssossssesasoseessossnesoens

Sediment and Surface Water Yields ....eeeeeeeeoeeoceonss

Relative Rates of Denudation in Uplands and Lowlands in
Different Climates ...viieerieeoenrennososossscsasssonnsns

Partial List of Highlands Uplifted in Pleistocene Time.

Page

11
22

25
26
27

28
29

52
52

L3
62
63

ol
65

66
70
Number

5.7
5.8
5.9
5.10

6.1

Al
A.2
A.3

Ak
A.5

LIST OF TABIES (contad)

Some Present Rates of Uplift .......... e escessensanenas
Greatest Known Fjord Depths ...veveiiernneeeennn ceseeaae
Present Rates of Glacial Erosion ......... ceen o ceeees .o

Geothermal Gradients at Selected Localities in the

United States .cevevvvnnnn... teeecssecceas o ssessseesanss
Possible Types of Deep-Seated Vertical Tectonic Move-

ments .seeee.. ceeesenas tessocecsrssnas cecssecssnacnnannne
Listing of Program FPDSOILS ....... oo Cevcecesceanoas
Listing of Program FPTSOILS .....cv000.e ce s e s e ceens
summary of Kd Values Used in Calculating Radionuclide

Movement ....ecveeeencsns crovssces ¢eosens beesseseranns o
Output of Program FPDSOILS ........... teveseasaans oo
Output of Program FPTSOILS «e.vieeesn.. Che e e e e s e

Vi

Tl

95
153
137

143
Lhl
Number

5.1

LIST OF FIGURES

Variation of Heat Generation Rate in Solid Waste with
Time After Discharge from Reactor ............ et

Predicted Movement of 9OSr from the Leaching of Pot
Calcine Material ...e.tieineeennnoseneeescnonsoonnens

Predicted Movement of 137Cs from the Leaching of
opray Melt Material ..... e e e e s s s eec s e s e e se st eansan

Predicted Movement of 259Pu from the Leaching of Glass
Having a Leach Rate Controlled by Diffusion of 10-2

I /B C 4 ettt et ettt ettt

Predicted Movement of 241Am from the Leaching of Glass

Having a Leach Rate Controlled by Diffusion of 107
2 S0 4 e e et et e e et ettt e ceeas

Cumulative Fraction of 9OSr Originally Present in Vari-
ous Forms of Waste That Would Reach a Seep 60 Meters
from the Source Under Conditions of Continuous Leaching

Cumulative Fraction of 157Cs Originally Present in
Various Forms of Waste That Would Reach a Seep 60
Meters From the Source Under Conditions of Continuous
LEACHING v et eet e tnneeetotesessonensasesotosossansasas

2

Cumulative Fraction of lAm Originally Present in
Various Forms of Waste That Would Reach a Seep 60
Meters From the Source Under Conditions of Continuous
ST ] 4 =

Cumulative Fraction of 259Pu Originally Present in
Various Forms of Waste That Would Reach a Seep 60
Meters From the Source Under Conditions of Continuous
Leaching e ettt it i i i e i e e i i e

Relation of Denudation Rates to Relief-Length Ratio
and Drainage Basin Relief ... ..ttt ieieeeeennnnns

Graph Showing the Dependence of the Average Velocity
of the Vertical Tectonic Movement on the Duration of
the Time Interval of AVEraging .e.eeeeeeeenesovnonsons

Average Relationships Between Shale Density and Depth.
North-South Structural Cross Section, Iowa Salt Dome..

Diagrammatic Cross Section of a German Salt Diapir and
Associated Rim Syncline .....c...iiiianesn. et ieoas cee

Mutual Relationships of Depth, Porosity, and Fluid
Pressure-Overburden Ratio in ar Average Shale or Mud-
S V)4 T

vii

Page

%0
L6

47

L8

L9

52

53

Sk

55

68

96
106
110

112

117
LIST OF FIGURES (contd)

Number Page

6.6(a) Diagrammatic Representation of the Development of a
Mud-Lump Family ..... ceseeeesas teesssseoan cesesaenne 120

6.6(b) Diagrammatic Representation of the Development of a
Mud-Lump Family .eceeeeeoecesesonnnsanns cheeeseanae 121

viii
CONSIDERATIONS IN THE LONG-TERM MANAGEMENT
OF HIGH-LEVEL RADIOACTIVE WASTES

 

 

Ferruccio Gera* and D. G. Jacobs

ABSTRACT

High-level radiocactive wastes generated by the
reprocessing of spent fuel elements in the projected
nuclear power industry require the development of an
organic waste management scheme. The presence in
these wastes of long-lived transuranics requires as-
surance of waste containment for a time period of the
order of several hundreds of thousands of years.

For such long time periods only deep geologic forma-
tions offer the stability required for preserving
the necessary degree of containment.

Projections are made of the amounts of radioac-
tive wastes accumulated to the year 2020. Important
radionuclides in the waste are compared on the basis
of their potential hazard to mankind over their en-
tire physical lifetime. On the basis of these con-
siderations, it seems that the most prudent scheme
of management of these wastes involves solidification
with final disposal into a suitable deep geologic for-
mation in such a manner that further handling will be
minimized.

The characteristics of products from various sug-
gested solidification processes are compared. The con-
ditions of interim storage of high-level solid waste
are reviewed, and possible mechanisms of activity re-
lease from the storage facility are considered.

In order to insure safe containment of the waste
for hundreds of thousands of years, the possible rate
of several geologic processes capable of affecting
the disposal formation must be estimated.

Possible mechanisms of activity release from the
deep geologic formation are described.

 

*Visiting scientist on leave from Italian National Committee for
Nuclear Energy.
1. INTRODUCTION

The nuclear industry is expected to expand rapidly during the next
few decades, and the processing of reactor fuels will result in accumula-
tion of much larger volumes of highly radioactive waste than have been
generated to date. It seems reasonable to assume that the overall scheme
of management will include a number of steps:

1. Interim storage as liquid.

2 Conversion to solid.

3 Interim storage as solid.

4. Transportation to an ultimate disposal site.

5 Ultimate disposal in a geologic formation.

In order to provide the basis for the development of a rational
policy for the management of these wastes, it is necessary to make pro-
jections concerning the quantities and characteristics of the wastes
that will be produced and to make an evaluation of the radiological
safety aspects of each of the steps enumerated above. Radiological
safety evaluations for the first four steps do not differ appreciably
from those encountered in most nuclear operations. However, because
of the increasing amounts of long-lived transuranics expected to be
present in future wastes and because of their potential radiological
hazards, the radiological safety evaluation for ultimate disposal in
geologic formations must consider extremely long time spans. Required
containment times are on the order of hundreds of thousands of years,
which is much longer than recorded human experience. Based on geologic
evidence, global climatic conditions may undergo extensive changes dur-
ing such time periods. Local geologic conditions might also be altered
significantly. '

No attempt 1s made in this report to establish criteria for the
long~term management of high-level radiocactive waste. Rather, the in-
tert is to elaborate on some of the many factors that must be considered
in the development of sultable criteria and to illustrate how several
of the environmental factors may be considered in determining their po-
tential impact upon a facility or upon the consequences of an activity -

release. If the consequences of a particular accident result in activity
- releases that cannot be tolerated, then the mechanisms responsible for
such a release must be evaluated to determine the likelihood of their
occurrence and the type of engineered safeguards that must be employed

to minimize the impact or reduce the activity release to an acceptable

level.
2. PROJECTED WASTE PROBLEM -

With the development of the nuclear industry assumed in Phase 3,
Case 42, of the Systems Analysis Task Force,g'l the amounts of waste
shown in Tables 2.1 and 2.2 will be accumulated in the United States
through the year 2020. These projections are based on a nuclear power
economy having both light water reactors and liquid metal fast breeder
reactors. Other advanced reactor types, such as molten salt reactors,
may require different waste management schemes.

259

The amount of transuranium isotopes, especially Pu, that will

be present in the wastes seems to dictate containment times far exceed-

ing the 1000-year period that would be necessary for the decay of 9OSr

157

and Cs, which have often been considered the radionuclides of major
hazard potential in long-term waste management. Tables 2.3 and 2.4 list
estimates of the amounts of transuranium isotopes that are expected in
the spent fuel of typical light water reactors (LWR's) and liquid metal
fast breeder reactors (LMFBR's) of the future. In Table 2.5 are shown
the total quantities of activity produced through the year 2020 for the
radionuclides that apparently control the long-term management of radio-
active wastes. The table shows that the amounts of transuranics cannot
be neglected. With the assumptions used in compiling Tables 2.1 and 2.2,
the solid waste from reprocessing of LWR fuel would contain 18 uCi/cm5
of 259Pu and 55 uCi/cm5 of 2LLOPu, assuming that 0.5% of the plutonium
present in the spent fuel is not recovered and finds its way into the
waste stream. These concentrations of plutonium correspond to 450 and
1375 maximum permissible body burdens (MPBB) per cubic centimeter of
solid waste. With the same recovery of plutonium from LMFBR fuel, the
solid waste would contain 190 uCi/cm3 of 259Pu (4700 MPBB/cm5) and 235

uCi/en® of 2Py (5900 MPBB/cm).
Table 2.1. Estimated Wastes from Light Water Reactors in the USA
(Modified from ORNL-LL51, 19702‘2)

 

Calendar Year

 

 

1980 1990 2000 2020
Installed capacity, 10° Mi(e)® 153 223 209 5l 1
Fuel processed, 10° tons/yearb’C 2.95 6.01 4.77 4.1
Volume of waste generated, as liquidd
Annually, 1o5 m : 3.67 7.49 5.98 17.5
Accumulated, 100 m 16.5 81.0 148. 4 330.8
Volume of waste generated, as solia®
Annually, o . 275 560 4hs5 1310
~ Accumulated, m 1245 6060 11,100 2L, 800
Accumulated radioisotopesf
Total weight, tons 451 2180 4000 8960
Total activity, megacuries | 18,900 54,500 62,550 142,700
Total heat-generation rate, 106 cal/sec  19.5 54 58 136
9OSr, megacuries 962 4340 7085 13,900
70s, megacuries 1280 5800 9530 18,900
258p,, megacuries® 1.20 6.3 11.6 2k.5
239py, megacuries® 0.022 0.107 0.196 0.438
240, megacuries® 0.0409  0.239 0.53 1.37
1o, megacuries® 6.63 07.7 40.3 7h. 1
EhlAm, megacuries® 2.31 11.3 20.8 46.6
3am, megacuries® 0.232 1.13 2.07 b. 62
2ung, megacuriesg 43,2 90 72 211
kb, megacuries® 29.9 130 200 379

 

. 2.1
®Data from Phase 3, Case 42, Systems Analysis Task Force (April 11, 1968)

bBased on an average exposure of 33,000 MWd/ton and a delay of 2 years be-
tween power generation and fuel processing: aqueous processing.

CThroughout this report metric tons are used (1000 kg or 2205 1lb).
dAssumes 1250 liters of liquid waste per ton of fuel.

5

®Assumes 1 m” of solid waste per 10.7 tons of fuel.

fpssumes fuel continuously irradiated at 30 MW/ton to 33,000 MWd/torn and
fuel processing 90 days after discharge from reactor.

€Assumes 0.5% of plutonium and 100% of americium and curium in waste.
Table 2.2.

2.2)

Estimated Wastes from Liquid Metal Fast Breeder Reactors in the USA
(Modified from ORNL-4451, 1970

 

Calendar Year

 

 

1985 1990 2000 2020
Installed capacity, 10° MW (e)® 28 145 546 1669
Fuel processed, 10° tons/yearb 0. 36 2.15 9.23 27.6
Volume of waste generated, as ].iquidC
Annually, 10° 0.447 2.69 11.L4 3.k
Accumulated, lO5 m3 0.939 9.1 79 570
Volume of waste generated, as solidd
Annually, m3 33 201 855 2570
Accumulated, m5 70 680 5920 42,590
Accumulated radioisotopese
Total weight, tons 25 260 2200 15,640
Total activity, megacuries 4388 30,000 146,450 523,300
Total heat-generation rate, 106 cal/sec 4.2 28 13k L66
9OSr, megacuries 31.8 300 2465 15,500 '
157Cs, megacuries 78.3 740 6070 38,600
238Pu, megacuriesf 0.18 1.98 9.1 141.5 .
2395y, megacuries® 0.013  0.128 1.1l 8.01 )
2”0Pu, megacuriesf 0.0161 0.156 1.38 10.0
2ulPu, megacuriesf 2.12 19.5 150.7 835
21‘LlAm, megacuriesf 1.18 11.4 100 716
21LBAm, megacuriesf 0.037 0.3%6 3,12 224
2u2Cm, megacuriesf 4.5 95 L15 1279
2uqu, megacuriesf 0.73 7 55 321

 

%Data from Phase 3, Case 42, Systems Analysis Task Force (April 11, 1968).2'l

bBased on an average exposure of 33,000 MWd/ton, and a delay of 2 years be-
agueous processing.

tween power generation and fuel processing:

“Assumes 1250 liters of liquid waste per ton of fuel.

5

dAssumes 1lm

of solid waste per 10.7 tons of fuel.

®Assumes core continuously irradiated at 148 MW/ton to 80,000 MWd/ton,

axial blanket to 2500 MWd/ton at 4.6 MW/ton, radial blanket to 3100 MWd/ton
at 8.4 MW/ton, and fuel processing 30 days after discharge from reactor.

fAssumes 0.5% of plutonium and 100% of americium and curium in waste.
Table 2.3.

in Light Water Reactor Fuel
(Burnup = 33,000 MWd/ton; Specific Power = 30 MW/ton;

90 days after discharge from reactor)

Amounts of Some Transuranium Isotopes

 

 

Specific
Content Activity Activity Half-1life

Isotope (kg/ton) (ci/g) (ci/ton) (years)
258Pu 0.16 17.2 2,780 88
239, 5.38 0.0613 330 24,413
Quopu 2.11 0.227 478 6,580
gulpu 1.10 105 115,800 14
Eugpu 0.36 0.00382 1.36  3.869 x 10°
g 0.050 3.1 172 432
2MAm 0.087 0.200 17.4 7,340
2“20m 0.006 3,320 19,300 0.45
b o 0.031 81.1 2,500 18

 

2.1 Potential Hazard Index

We have attempted to compare the potential hazards for mankind re-

sulting from the presence in high-level waste of several nuclides hav-

ing long half-lives.

the PHI (Potential Hazard Index), defined as:

2.3,

2.4

In order to make this comparison, we

T.
1

" 0.693

total activity of nuclide i (uCi),

Maximum Permissible Annual Intake of nuclide i (uCi), and

introduce
Qi
PHL; = Py Wor.
i
where
Qi =
MPI. =
i
T, =

physical half-life of nuclide i (years).

Pi 1s a factor dependent on the biological availability of radionuclide

i once it is dispersed into the environment and on the reliability of
Table 2.4. Amounts of Some Transuranium Isotopes in Liquid Metal Fast Breeder

Reactor Fuel

(Burnup

= 33,000 MWd /ton; Specific Power™
= 58 MW /ton; 30 days after discharge from reactor)

 

 

opecific
Content Activity Activity Half-1life

Isotope (kg/ton) (ci/g) (ci/ton) (years)
258Pu 0.65 17.2 11,220 88
239py 57. 42 0.0613 3,530 2h,h13
guoyu 18.77 0.227 L ,260 6,580
2kl 5.71 105 600,000 1
242 5

Pu 3.%3% 0.00382 13 3.869 x 10
A lpm 0.46 5.1, 1,570 430
2”5Am 0.25 0.200 50 7,340
o2
h Cm 0.02 3320 65,500 0.45
ko 0.015 81.1 1,240 18

 

a . .
Fuel is mixture of core + blanket; burnup

values for the mixture.

and specific power are average
Table 2.5. Potential Hazard Index of Several Significant Radionuclides
Accumulated in High-Level Solid Waste by the Year 2020

 

 

 

 

MPI's in Wastea | Potential Hazard Index
Quantity
Nuclide (ci) Ingestion Inhalation Ingestion Inhalation
At Year 2020
Pgp 2.9 x 1010 9.0 x 10-° 1.0 x 1016 3.6 x 107" u.0 x 10Y7
157Cs 5.7 X lOlO h.7 x 101“ 3,6 x lOlL‘L 2.0 x 1016 1.5 x 1016
28p® 17 x10° k2 x 102 s ox 10 5.3 x 0% 4.3 x 1018
239Pu 8.4 x 106 2.3 x lO]'l 2.1 x lO15 8.1 x 1015 7.h x 1019
MOpt 15 %100 3.6 x 10t 3.2 x 10%7 34 x 1087 3.1 x 1019
QulAmd 7.9 x 108 2.6 x lO15 5.3 x 1016 1.6 x 1016 3.3 x 1019
M 2.7x 100 7.7 x 108 1.9x 108 8.2 x 10" 2.0 x 109
After 300 Years Decay

Pgr 1.6 x 10/ 5.0 x 10%° 5.5 % 10 2.0 x 1olu 2.2 X lolu
157Cs 5.7 x 107 h.7 x lOll 3.6 x lOll 2.0 x lO13 1.5 x lO]'5
258Pu 1.6 x 107 4.0 x 10™F 3.2 x 101° 5.1 % 1017 .1 x 10%
259Pu 8.4 x 106 2.% x lOll 2.1 x lO15 8.1 x lO15 7.4 x 1019
M0p, 1.3 x 107 3.6 x 10 32x 1080 34 x 1087 3.1 x 1019
2LLlAm 5.0 x 108 1.7 x lO15 5.5 x 1016 1.1 x 1016 2.1 x 1019
Mam 2.7 x 107 7.7 x 1077 1.9 x 1077 8.2 x 102 2.0 x 107

 

®MPI is the Maximum Permissible Annual Intake.

242 258Pu.

bAssumes all Cm decayed to

“Assumes all guqu decayed to 240Pu'

qusumes all gulPu decayed to 2ulAm.
10

waste containment, and represents the probability of the nuclide leaving

the disposal site and reaching man. Presently, we are not able to give

the probability of exposure, and therefore in Table 2.5, P is taken equal
Q.

to 1 for all radionuclides. MP% is the number of Maximum Permissible
i

Annual Intakes of nuclide i present in the waste, and the hazard is con-
sidered to be proportional to this value. The MPI was chosen instead of
the Maximum Permissible Organ Burden Equivalent (a Maximum Permissible
Organ Burden Equivalent is the quantity of a radionuclide that must be
introduced into the body to result in the retention of a Maximum Permis-
sible Organ Burden in the critical organ), because equivalent dose com-
mitments are considered the most satisfactory expression of equivalent
risks.

The mean life (Ti/O.695) is a measure of the time span during which
the radionuclide will exist and is important in determining the potential
global hazard. Normally, when one 1s concerned with radiological hazards
to individuals, the exposure period of concern is limited to 70 years.
However, when exposure of mankind is considered, the potential hazard
can be considered to last for the physical mean life of the radionuclidex*.
Two PHI values are obtained, one for ingestion and one for inhalation;

these two values can differ by as much as four orders of magnitude.

2.2 Potential Hazard from Plutonium Isotopes

In the case of inhalation, the Potential Hazard Indexes for several
transuranium isotopes are greater than those for cesium and strontium.
In relation to the hazard from inhalation of plutonium, several authors
have argued that the MPC and the MPI presently used are too high. Ap-
parently, in the case of inhalation of insoluble plutonium, the highest

dose 1s absorbed by the tracheo-bronchial lymph nodes. There is also

 

*For the sake of simplicity, the contribution to the potential haz-
ard from the daughter nuclides has been neglected. However, when the
decay chain of a nuclide includes hazardous daughters, the PHI should be
modified to consider the additional potential hazard.
11

- evidence that substantially less plutonium reaches the skeleton than is
assumed in ICRP Publication 2.2'5 According to Voillequé, Shleien, and
others, the dose to the tracheo-bronchial lymph nodes is orders of magni-
tude higher than the dose to other organs.2'6_2'8 In Table 2.6 are
listed 50-year dose commitments to various organs for the intake of 1

uCi of 259PuO

5y @S calculated by Voillequé. With the assumptions and
constants used, an intake equal to the present Maximum Permissible Annual
Intake (occupational = 0.0043 uCi) would result in a 50-year dose commit-

ment to bone of 1.1 to 2.0 rem, depending on the value assumed for the

Table 2.6 Fifty-Year Dose Commitments Resulting
From the Inhalation of 1 uCi of 239PuO

’ 2.6 2
(Data from Voillequé, 19687 ")

 

50-Year Dose Commitment (in rem) for Activity Median
Aerodynamic Diameter (AMAD) of:

 

 

Organ 0.05 um 0.10 um 0.50 um
Lymph nodes 260,000 221,000 132,000
Lungs 1,160 980 588
Liver 497 Lok 277
Bone L71 Lo2 262
Kidney 97.5 ' 83.2 5Lh.3

 

activity medium aerodynamic diameter (AMAD). The same intake would re-
sult 1n a dose commitment of 570 to 1120 rem to the lymph nodes and from
2.5 to 5 rem to the lungs. If these considerations are valid, the MPC
for inhalation of plutonium should be recalculated with the lymph nodes
as the critical organ. With a MPD to lymph nodes of 15 rem/year (which
is the MPL for unspecified body organs), the MPC would be lowered to
10"lLL uCi/cmi, with an equivalent MPI of 7 x 107~ uCi (calculated for an
AMAD of 0.1 u). With the reduced value for the MPI, the Potential Hazard

Indexes in Table 2.5 for inhalation of plutonium isotopes would be in-

creased about two orders of magnitude. The whole question of dose to
12

respiratory lymph nodes and of recalculation of MPC for inhalation of
plutonium is rather controversial and has been reviewed recently by the
ICRP.2'9 The main points of the problem are briefly summarized as fol-
lows. The mechanism of clearance from the lungs results in accumulation
of particles of insoluble plutonium in the respiratory lymph nodes. The
clearance from the lymph nodes i1is nonexistent or extremely slow; there-
fore, the lymph nodes can be considered as a "sink.'" The total mass of
the lymph nodes in question is about 10 g, and this gives rise to the
very high local doses reported. If the exposure were averaged over the
total mass of the complete lymphatic system (about 700 g), the average
dose to the lymph system would be almost two orders of magnitude lower.
This procedure might be justified in consideration of the lymph circula-
tion, but the noncirculating tissues of the lymph nodes will receive
much higher exposure. Perhaps further long-term experimentation will
indicate that respiratory lymph nodes are not so sensitive to radiation
as to require limitation to an annual MPD of 15 rems. The Task Group

on Spatial Distribution éf Radiation Dose of Committee I, International .
Commission on Radiological Protection, has recently commented on this
problem and expressed the opinion that a change in the dose limit for
plutonium on the basis of risk to the lymphoid tissue is not warranted

2.9

at the present time.

2.5 Comparison of Inhalation and Ingestion Hazards

Going back to the Potential Hazard Index, we realize that two values
for each radionuclide have little meaning and that they should be combined
to give a total Hazard Index. Theoretically, each should be weighted by
a factor representing the probability that the dose will be delivered
to man through ingestion or inhalation. Unfortunately, the statistically
valid data on the long-term behavior and distribution of the significant
radionuclides in the environment that would be necessary for a meaningful
comparison of ingestion and inhalation hazards are not available. .

The only information on global behavior of radionuclides is derived
from fallout data. However, the usefulness of fallout data to evaluate

the possible behavior of radionuclides originally present in solid waste
15

is somewhat limited. The main problem is that fallout radioactivity is
initially released to the atmosphere in finely divided particles; there-
fore, the importance of inhalation is greatly stressed. From the data
available in the literature, however, it can be concluded that even in

this situation only a small fraction of the total intake is from inhal-

2.10-2.12 90

ation. The amount of Sr taken into man through the food

chain is 25 to 50 times higher than the amount inhaled. Fifty to one
137 239,

hundred times more
4 240

Cs 1is ingested than inhaled. The intake of
an Pu by ingestion is only two to four times higher than the intake
by inhalation. In the case of fallout, it is possible to assume that
inhalation is a direct pathway with an intake proportional to the quan-
tity of radionuclide present in the atmosphere. With this assumption,
the different ratios of ingestion to inhalation can be used to indicate
relative transfer coefficients of the various radionuclides along the
food chains. Transfer coefficients for strontium and plutonium will be
0.5 and 0.0k, respectively, of that for cesium. These relative transfer
coefficients are dependent on deposition and suggest foliar interception
as a primary mechanism of entry into the food chains. If the major frac-
tion of the activity reached the ground, one would expect the transfer
coefficients to be much different. Cesium, for example, 1s normally
quite efficiently restricted in its transfer to crops because of its
selective absorption onto soil minerals, but it is quite mobile in bio-
logical systems.2 15

At this time the problem of introducing factors to weight the con-
tributions to total hazard related to ingestion and inhalation seems
exceedingly complex. However, even considering the low mobility of plu-
tonium and americium through food chains, it seems that their content
in high-level waste is such that exclusion from the biosphere will be
required for times greatly in excess of the time period necessary for
decay of cesium and strontium. A decay period of a quarter of a million

259Pu by only three orders of magnitude.

years will reduce the amount of
If such long decay times are necessary, there is no man-made structure
that can be guaranteed to provide safe containment. Because the relative
seriousriess of the potential hazard from plutonium due to inhalation 1is

so much greater than that due to ingestion, we believe that the most
14

prudent scheme of management would be to dispose of the wastes in a suit-
able geologic formation in such a way that further handling will be mini-
mized. It also seems certain that the waste to be disposed of will be
in solid form and that every attention will be given to using as little

space as possible in the geologic formation chosen for ultimate disposal.

2.4 Steps in High-Level Waste Management

The considerations discussed in the previous section imply that the
management of high-level radiocactive waste will include the following
steps, starting at the exit of the fuel processing plant.g'2

1. Interim Storage as Liquid. Liquid storage before solidification

 

will be necessary to allow the decay of very short-lived radionuclides.
This storage will be on the site of the reprocessing plant in underground
tanks. The alternative solution of storing irradiated fuel for a suit-
able period before reprocessing would result in increased fuel cost, but
it should be evaluated in relation to the possible reduction in risk.

2. Conversion of Waste to Solids. At the present time 1t seems

 

that high-level wastes produced at reactor fuel reprocessing plants will
have to be converted into solids. Solidification processes are being
studied in many countries and should eventually become common practice.
Solidification is believed to reduce appreciably the risk associated with
the storage of waste and is required for safe transport of waste. The
Savannah River proposal of disposing of high-level liquid waste in a
vault excavated in crystalline bedrock at the depth of about 450 m may

be feasible for their present high-level wastes in the particular
geologic situation of the Savannah River plant.g'llL However, such a
scheme would rnot be acceptable for the large amounts of waste that will

be produced by the nuclear industry of the future.

5. Interim Storage as Solid. This step is not very well defined;

 

several technologies have been proposed, such as storage in water-filled
canals or basins, in air-cooled annular bins, in air-cooled concrete
vaults, or in alr-cooled wells. Undoubtedly, other management schemes
are possible and will be proposed. Interim storage as solid is necessary

to allow radioactive decay of most activity of radionuclides with short
15

and intermediate half-lives. After some storage period the wastes will
have a reduced heat generation so that efficient utilization of space in

215 The interim stor-

the ultimate disposal formation will be possible.
age of solid wastes will probably be on the site of the reprocessing
plant.

L. Transportation of Waste to the Site of Ultimate Disposal. Trans-

 

portation of wastes through unrestricted areas could be avoided only if
the processing plant were located on the site of the disposal formation.
However, the number of reactor fuel reprocessing plants will likely ex-
ceed the number of ultimate disposal facilities, and it appears that in
most cases transportation of solidified waste will be required.

5. Ultimate Disposal in a Geologic Formation. At the present time

 

the most reasonable approach to the problem of ultimate disposal is to
store solidified wastes deep in the terrestrial environment to ensure
that they are not reached by circulating groundwater during the time re-
quired for decay of their radioactivity to innocuous levels. Nuclear
transmutation and extra-terrestrial disposal are theoretically possible,
but neither seems to offer a practical solution to the waste-disposal

problem at this time.

2.5 Evaluation of Risks Associated with Waste Management

The final decisions on the relative lengths of the interim storage
periods as liquids and as solids and on the siting of reprocessing plants
will be controlled by a balance between minimizing risk and minimizing
cost. In comparison with risk evaluations, cost evaluations are much
easier, and they provide guantitative answers. Risk evaluations, on the
other hand, are often based on subjective elements.

The total risk associated with radiocactive waste management will
be the sum of risks encountered in each of the five steps mentioned
above. It is clear that the main goal of radioactive waste management
must be to reduce this cumulative risk to the lowest practicable level.
The five steps contribute to the total risk differently, and the evalu-
ations of the five contributions to risk do not present the same degree

of difficulty. The risks associated with tank storage, solidification,
16

and transportation have been evaluated in some detail or their evaluation
seems to present minor difficulties.g'2 ~
Little information is available to permit an adequate evaluation of .
the risks associated with the interim storage as solid, since no such .
facility is in existence at the present time. The risks related to the
ultimate disposal in a geologic formation are much more difficult to
assess. Later, we will try to indicate some of the geologic questions
that must be answered before a geologic formation can be considered
suitable as the ultimate recipient of high-level waste. So far, most of

the research work done in relation to the ultimate disposal of high-~level

waste has been involved with rock salt.

2.6 Advantages of Disposal in Salt Formations

Oak Ridge National Laboratory has completed a successful demonstra-
tion at the Lyons salt mine in Kansas of the feasibility of disposal of

2.16, 2.17 The advantageous characteristics e

highly radioactive wastes.
of salt have been discussed in detall by many authors; however, we will
repeat here some of the main points: .
1. ©Salt 1s plastic and, therefore, all cavities, openings, and
fractures are self-sealing.
Salt has good thermal conductivity.
Salt is cheap to mine and is geographically widespread. Be-
sides, there are many abandoned salt mines that may be suitable
for the disposal of high-level solid Waste.g'18
The solubility of salt, which in itself is not an advantageous
feature, does permit to demonstrate that circulating groundwater has
never reached the levels where salt has been preserved for millions of
years.
At the present level of technology, disposal of high-level solid
waste in bedded salt formations seems to be the safest available solu-
tion. However, we feel that one of the steps in the realization of an
actual disposal facility in salt should be a review of geologic parame-
ters relevant to the problem of waste containment for a time period of .

several hundred thousand years. Such a review is planned for the pro-

posed prototype facility in bedded salt.
17

2.7 Retrievability of Stored Wastes

If a salt formation has been thoroughly investigated and found suit-
able for the disposal of radioactive waste, it is implied that all geo-
logic data indicate that no change capable of impairing waste containment
is foreseeable in a time period of several hundred thousand years. Under
these conditions, we consider it unnecessary to consider retrieval of the
waste. Certainly retrievability from salt is possible, but it might be
a rather complex operation. ©OSteel containers have a very limited life in
salt; stainless steel containers are expected to last about 6 months,
while mild steel in that particular environment should last a few years.
However, at the time of retrieval, containers would probably have lost
their integrity and the waste would have to be mined out. We feel that
this operation would pose additional radiological problems and would be
expensive. Disposal in salt should really be considered as "ultimate."
If the waste management scheme must include retrievability as a necessary
condition, some alternative to salt disposal should be investigatedf For
example, a deep, dry mine in a geologic material different from salt in
a geologically stable area might be a desirable solution if long-term

integrity of waste containers needs to be assured.

2.8 References

2.1. Phase 3, Case 42, Systems Analysis Task Force (April 11, 1968).

2.2. ORNL Staff, Siting of Fuel Reprocessing Plants and Waste Manage-
ment Facilities, ORNL-4L51 (1970).

2.3, K. Z. Morgan, W. 3. Snyder, and M. R. Ford, "Relative Hazard of
the Various Radiocactive Materials,” Health Phys. 10, 151-168 (196L4).

 

2.4. R. A. Hilliar, Relative Inhalation Hazards from Nuclides Present
in Fresh Irradiated Fuel, RD/B/N-1143 (1968).

2.5. P. J. Magnus, P. E. Kauffman, and B. Shleien, "Plutonium in En-

 

vironmental and Biological Media," Health Phys. 13, 1325-1330
(1967).
2.6.

2.7.

2.8.

2.9.

. 10.

.11,

.12,

.13,

.1k,

.15.

.16.

18

P. G. Voillequé, Calculation of Organ and Tissue Burdens and Doses

 

Resulting from an Acute Exposure to a Radioactive Aerosol Using the

 

TCRP Task Group Report on the Human Respiratory Tract, 1D0-12067
(1968).

B. V. Anderson and I. C. Nelson, "Measurement of Plutonium Aerosol

 

Parameters for Application to Respiratory Tract Models,"

Symposium
on the Assessment of Airborne Radioactivity in Nuclear Operations,

TAEA, Vienna, 3-7 July 1967.

 

B. Shleien, "An Evaluation of Internal Radiation Exposure Based on
Dose Commitments from Radionuclides in Milk, Food, and Air,"
Health Phys. 18, 267-275 (1970).

International Commission on Radiological Protection, Radiosensi-

tivity and Spatial Distribution of Dose, ICRP Publication 1k,

 

Pergamon Press, London, 1969.
U. S. Department of Health, Education, and Welfare, Radiological
Health Data and Reports, Volumes 1 to 11, 1960-1970.

 

 

 

Report of the United Nations Scientific Committee on the Effects a
of Atomic Radiation (UNSCEAR), General Assembly: 17th Session,
Supplement No. 16 A/5216; 19th Session, Supplement No. 1k Z/581L; .

21lst Session, Supplement No. 14 A/631L.

Cl. Stidvenart and E. Van Der Stricht, L'évolution de la radioac-

 

tivitd ambiante au cours des anndes 1962 & 1966 et ses cons€quences
pour la contamination radioactive de la chalne alimentaire, EUR
Lhol12 (1968},

K. Z. Morgan et al., Health Phys. Div. Ann. Progr. Rept. July 51,
1969, ORNL-4LL6, pp. 76-111.

 

J. F. Proctor and I. W. Marine, "Geologic, Hydrologic, and Safety

Considerations in the Storage of Radioactive Wastes in a Vault

 

Excavated in Crystalline Rock,” Nuclear Science and Engineering 22,

350-365 (1965). |

F'. Birch, Thermal Considerations in Deep Disposal of Radioactive

Waste, NAS-NRC Publication 558 (1958). v
R. L. Bradshaw, J. J. Perona, J. O. Blomeke, and W. J. Boegly, Jr.,
Evaluation of Ultimate Disposal Methods for Liquid and Solid Ra-
dioactive Wastes: VI. Disposal of Solid Wastes in Salt Formation,

ORNL-33%58, Rev. (1969).
2.17.

2.18.

19

W. C. McClain and R. L. Bradshaw, "Status of Investigations of
Salt Formations for Disposal of Highly Radioactive Power-Reactor
Wastes," Nuclear Safety 11, 130-1k1 (1970).

Committee on Waste Disposal of the Division of Earth Sciences,
The Disposal of Radioactive Waste on Land, National Academy of

Sciences-National Research Council, Publication 519 (1957).
20

5. CHARACTERISTICS OF SOLIDIFIED HIGH LEVEL WASTES

There are several laboratories where the solidification of high-level
waste has been or is being investigated. Six solidification processes,

and even more solid compositions, have been proposed.B'l’ 5.2

Fluidized
bed calcination has been successfully demonstrated in actual operation in
the Waste Calcining Facility (WCF) at NRTS, Idaho.5'5 The Marcoule So-
lidification Plant began operations in 1969 and is eventually expected to
convert to solids all high-level liquid waste stored at that site. At
Hanford in the Waste Solidification Engineering Prototypes four different
solidification processes and the solids obtained have been evaluated.B'2
However, at the present time, not all results of the solid-waste evalu-
ation tests are in comparable form, and not enough data are availlable for
solids made from actual waste.

The solidified waste characteristics that can be of importance for
the safety of storage are: |

1. leachability (by water, air, or vapor),

2. thermal conductivity, and

3. chemical stability and resistance to radiation.
Leachability controls the rate with which the activity contalined in the
solids becomes available for transport by the leaching medium, 1f failure
of the other containment systems should occur. Thermal conductivity de-
termines the heat production that can be tolerated in solids when the
maximum center line temperature and the dimensions of containers have
been defined. Thermal conductivity controls the thermal history of the
solids and, therefore, affects their leachability. Chemical stability
and resistance to radiation should be such that no gas is generated dur-
ing storage and that the characteristics of the solids remain fairly
constant. Resistance and mechanical strength are of importance during
handling, transportation, and the initial period of storage.

In normal operations the waste will be transported to the ultimate
disposal site while the container is still intact, so that during interim
storage no activity will be leached regardless of the leachability of the

solids. It is possible to imagine accidental failure of a container due >

to increased corrosion rate or to lack of intervention at the right time.
21

. In the event of container failure, waste mobilization, if it is possible,
will be controlled by the leachability or by the heat production rate to
such a high degree that the other waste characteristics can be neglected.
Known physical and chemical characteristics of the solids obtained
by solidification processes proposed so far are shown in Table 3.1. Be-
cause of the difficulty of comparing data obtained by different labora-
tories with nonuniform experimental procedures and occasionally with
contradictory results, the figures in the table should be considered only
as indicative of relative orders of magnitude, and even more so consider-
ing that very little information is available about actual waste solids
and that the experimental procedures reproduce very poorly the expected

disposal conditions.

5.1 Leachability

The available leach rates were all determined with water, and most
of them were measured at room temperature. These leach rates are intended
to be representative of long-term leaching, and therefore they are the
rates reached after some time, disregarding the high leach rates observed
in the initial leaching period.B'u_5'6
| Solids produced by calcination show very high solubility; spray melt
solids are intermediate; and glasses have the lowest leach rates. How-
ever, even with glass, serious problems of water contamination could
arise. TFor example, if a glass cylinder, 30 cm in diameter and 183 cm
long, were exposed daily to leaching over its entire surface by a volume
of water equal to the volume of glass and if the initial level of fission
product activity contained in the cylinder were a few million curies,
after 50 years of storage the activity in leach water would still be well
above permissible levels for drinking water.5'8

The leachability of glass is affected by a number of factors. The
porosity and the presence of fractures affect the total leach rate from
the solid by increasing the total area exposed to leaching. The cooling
rate of the solids affects their leachability; slow-cooled glasses are
more soluble than fast-cooled ones. The glasses produced from actual

waste probably will be cooled faster than lOC/min at the surface, but the

interior of glass cylinders will cool very slowly because of continuing
 

 

 

 

 

 

Table 3.1. Characteristics of Solidified High-Level Waste
1 2 3 L 5 6 7
Pot Phosphate Fingal and
Process Calcination Fluid Bed Spray Melt Glass Others Marcoule Chalk River
Silico-boro- Nepheline-
Ceramic or Phosphate Boro-silicate phospho-molyb- syenite
Product Calcine Granules Glass - Glass Glass dic Glass Glass
Thermal Conductivity
(1072 cal/sec/em/C) 0.8 o ~ 3.0 (25°%C) ~ 3.0 (25°C)
o 2.87 (657¢C) o o
0.41 (100°¢) o ~ 2.4 (1007C) 3.06 (100°C)
o 2.39 (200°C) o
0.58 (300 C) 3.33 (300 C)
0.48 (5oooc) 3.66 (50000)
0.97 (700°C) o o k.08 (700°C)
3.0 (800°¢C) ~ 3.2 (800°C)
(range) 0.62 to 1.03 0.4k1 to 1.03 1.65 to 3.31 2.07 to 4.13
Maximum Heat
Production
(1072 cal/sec/cmB) 2.0 1.7 4.8 5.3
Bulk Density
(g/cm3) 1.1 to 1.5 1.0 to 1.7 2.7 to 3.2 2.7 to 3
Leachability by
Water
2
(g/cm”/day)
25 to 30°C 5 x 107% 5 x 107% 1tos5x10% 5x10° s lx 1076 5 x 1070 1x 1077
o 1 tos x 10
0 to 100 C -La
20 to {} to 5 x 10 4 }

 

aThe leachability of phosphate glass is strongly dependent on storage temperature.

vitrified, show much higher leach rates.”*

Samples stored at 600°C, and

therefore de-

2c
25

. heat generation due to radioactive decay. Therefore, the solid will
grade in solubility (and possibly in composition) between the rapidly
cooled glass next to the container wall and the slowly cooled glass in
the center. The chemical composition of the glass also affects the solu-
bility; the higher the alkali content, the higher the solubility.

The temperature of leaching is a major factor; the leach rate in-
creases by a factor ranging from about 10 to more than 100 if the tem-
perature is increased from,25oC to the range 95 to 100°C. Besides this,
it seems that at high temperature the leach rate remains constant with
time, while at room temperature there is an initial high leach rate that
decreases for as long as a year before it reaches a steady value.B'9 The
age of the glass at the beginning of leaching and the storage conditions
have some effect on the leach rate. Older glass leaches at a higher
rate. Glasses stored in air at 100% relative humidity show much higher
leachability than glasses kept in dry air or under water.B'lo The effect
of the leaching solution composition is not clear; experiments made at
Pacific Northwest Laboratory show higher leach rates in well water than
in distilled water. On the other hand, leach experiments conducted at
Harwell with distilled water and simulated seawater failed to show any
appreciable difference between the two.B'll’ >-12

Different elements can be expected to be leached from the glass at
different rates, at least at room temperature. There is evidence that
cesium is more leachable than strontium, and both these elements are much
more leachable than cerium. No data are available for plutonium leach
rates. However, at high temperature all differences in leach rates among

elements tend to disappear, because the leaching process becomes con-

trolled by the increased rate of glass corrosion.

5.2 Heat Generation Rate

The considerations that follow assume that the waste after solidifi-
cation is in the form of glass and is contained in stainless or mild steel
cylinders. The dimensions of the cylinders are controlled by the heat-
generation rate and by the thermal conductivity of the glass. The heat-
generation rate in any amount of waste at any time is a function of the

initial characteristics and of the age of the waste.
2l

In Table 3.2 are shown some typical chemical compositions of the
inert materials in high-level liquid wastes. Compositions 1 and 2 are :
for fairly dirty wastes (that is, they contain substantial amounts of .
inert materials); composition 3 is for a clean waste that can be expected -
to be representative of the waste produced in the near future. 1In Table .
3,% are shown the amounts of major materials from nuclear fission for
different fuel exposures in LWR's. Let us consider now the glass formed
by the solidification of these wastes. At the moment it seems that a
phosphate glass of good quality cannot contain more than 20 to 25% by
weight of waste oxides, and we will assume that this holds for other glass
types as well. With the assumptions used to assemble Table 2.1, a cublic
meter of solid waste will be produced for every 10.7 tons of fuel.

In the case of LWR fuel exposed to 55,000 MWd/ton at the power level
of 30 MW/ton, we obtain respectively 730 and 4LO kg of waste oxides per
cubic meter of glass for compositions 1 and 3 of Table 3.2. Considering
the bulk density of the glass to be 2.8, we obtain a waste oxlde content,
in the two cases, of 26% and 16% by weight. Very likely when wastes be-
come as clean as the one in column 3 of Table 3.2, a cubic meter of glass
will be able to accommodate waste from more than 10.7 tons of fuel. In -
such case the period of interim storagé as liquid will need to be propor-
tionally longer, if a heat-generation rate of 5 x 1072 cal/sec/cm5 is not
to be exceeded in the solidified waste. This heat-generation rate has
been assumed for calculation of storage container dimensions for interim

5.15

storage. In Tables 3.4 ard 3.5 are shown the heat-generation rates

in waste from the reprocessing of 1 ton of LWR fuel and 1 ton of LMFBR
fuel, respectively.E'lLL

In Table 3.6 and Fig. 3.1 are shown the heat-generation rates in
solid wastes, derived from different fuels, at various times after re-

processing. Assuming a limit in heat-generation rate of 5 x 10-2

5

cal/sec/cm”, for the waste of Table 3.6, column 2, solidification would
be possible between 5 and 6 months after discharge from the reactor; for
the wastes of columns % and 4 solidification would be possible about 8
months after discharge from the reactor.

If we further assume that the average thermal conductivity of the
slass is 5 x 1077 cal/sec/cm/°C and the specific heat is 2 x 107t cal/g/C

. -1
(~ 5.5 x 10 cal/cmB/OC), we can estimate the thermal conditions of the
25

Table 3.2. Range of Chemical Compositions of High-Level Liquid Waste
(Modified from Schneider, 19685'2)

 

Concentration, Molarity (@ 378 liters/ton

 

Constituent No. 1 No. 2 No. 3

 

General Chemical Composition of Inert Materials

 

 

 

 

 

 

Na Low High Low
Fe High Medium Low
Al 0 0 0
80, 0 0 0
Actual Chemical Composition of Inert Materials
H 3.7 5.95 6.29
Fe 0.93 0.4h5 0.05
Cr 0.012 0.024 0.012
Ni 0.005 0.010 0.008
Al 0.001 0.001 0.001
Na 0.138 0.93 0.10
U 0.010 0.010 0.010
Hg < 0.001 < 0.001 < 0.001
No5 7.5 5.37 6.66
80, _———— 0.87 -
Pou 0.003 0.006 0.003
Sio5 0.010 0.010 0.010
F < 0.001 < 0.001 < 0.001
a
> M 3. 0% 2,48 0. 365
Kg oxide/tor 31.7 28.lb L.6

 

vt is metal equivalents, or normality of metal ions (does not
include acid).

bDoes not include the sulfate. If sulfate is not volatilized,
approximately 27 kg/ton of additional oxides are formed.
Table 3.3. Chemical Composition of Major Materials from Nuclear Fission
(Modified from Schneider, 19683-2)

 

Fuel Exposure in Thermal Reactors

 

 

20,000 MWd/ton 33,000 MWd/ton 45,000 MWd/ton

Constituent 15 MW/ton 30 MW/ton 30 MW/ton
Mo 0.065 0.095 0.130
Te 0.01k4 0.023 0.031
Sr 0.0155 0.026 0.036
B3 0.0195 0.030 0.041
Cs 0.035 0.057 0.078
Rb . 0.007 0.010 0.01kL
Y + RE 0.12 0.201 0.27h4
Zr 0.0063 1 0.105 0.143
Ru 0.03%2 0.06 0.082
Rh 0.0074 0.009 0.013
Pa 0.017 0.031 0.043
Ag 0.0008 0.0012 0.0016
cd 0.0008 0.0018 0.0005
Te 0.006k 0.010 0.01k4

+ D
> M fp 0.91 1.27 1.73
kg oxide/ton 22 36 49

 

aRE is rare earth elements.

bM+ 1s metal equivalents, or normality of metal ions (does not

include acid).

92
Table 3.L4. Heat Generation Rate in the Waste from the Reprocessing
of 1 Ton of LWR Spent Fuel (cal/sec/ton)

 

Fuel Exposure

 

 

 

Time After 33,000 MWd/ton; 30 MW/ton 45,000 MWd/ton; 30 MW/ton
Discharge from - a ) 5 S D
Reactor Fission Products Actinides Total Fission Products Actinides Total
90 days 6260 193 6L 50 8540 263 8800
120 days 5310 172 5480 7240 23l TLT70
150 days 41610 154 L770 6290 210 6500
180 days 4060 139 4200 5540 189 5730
1 year 2390 75 2L 60 3260 102 3360
3 years 810 2 83k 1100 33 1140
10 years L6 17 263 335 23 358
30 years 135 9 1hh 184 12 196
100 years 24.9 2.4 27.3 3%.9 3.3 37.2
300 years 0.26 1.28 1.53 0.35 1.74 2.09
1000 years < 0.01 0.54 0.5 < 0.0l 0.7h 0.74

 

aTotal fission product power less noble gases and iodine.

bBased on 0.5% of plutonium and 100% of other actinides in waste (fuel processed 90 days after
discharge from reactor).

L2
28

Table 3%.5. Heat Generation Rate in the gaste from the Reprocessing
of 1 Ton of LMFBR Spent Fuel  (cal/sec/ton)

 

Fuela Exposure

 

 

 

Time After 33,000 MWd/ton; 58 MW/ton
Discharge from 5 S
Reactor Fission Products Actinides Total
30 days 19,100 77 19,200
60 days 13,200 65 13,200
90 days 10,300 60 10,400
150 days 7,240 50 7,290
1 year 5,300 30 5,530
3 years 860 17.5 878
10 years 181 16.6 198
30 years 105 15.8 121
100 years 20.5 13.4 33.9
300 years 0.36 9. 30 9.66
1000 years 0.01 ' 5.30 5.51

 

aFuel is mixture of core + blanket.
bTotal fission product power less noble gases and iodine.

“Pased on 0.5% of plutonium and 100% of other actinides in
waste (fuel processed 30 days after discharge from reactor).
Table 3.6. Heat Generation Rates in Solid Waste (cal/sec/cm5)

 

 

 

Time After LWR Waste™ LMFBR Wastel
Discharge from
Reactor 33,000 MWd/ton; 30 MW/ton 45,000 MWd/ton; 30 MW/ton 33,000 MWd/ton; S8 MW/ton
30 days 2.1 x 107+
60 days 1.4 x 10"
90 days 6.9 x 10°° 9.4 x 1072 1.1 x 107"
120 days 5.9 x 107° 8.0 x 10°°
150 days 5.1 x 1072 6.9 x 107° 7.8 x 1077
180 days 4.5 x 1077 6.1 x 10°°
1 year 2.6 x 107° | 3.6 x 1072 3.6 x 1072
3 years 8.9 x 107 1.2 x 1077 9.4 x 1077
10 years 2.8 x 107 3.8 x 107 2.1 x 1077
20 years 1.9 x 1077 2.6 x 107 1.5 x 1077
30 years 1.5 x 107 2.1 x 1077 1.3 x 1077
100 years 2.9 x o7t 4.0 x 107 3.6 x 1o
300 years 1.6 x 1077 2.2 x 1077 1.0 x 107%
1000 years 5.8 x 10'6 7.9 x 10'6 3.5 x 10”7

 

5

aAssumes 1 m” of solid waste per 10.7 tons of fuel.

bAssumes 1 m5 of solid waste per 10.7 tons of fuel (core + blanket).

62
50

ORNL-DWG 69-6862R

-sec-Y-cm-3

cal
o

Y|N ALL THREE CASES IT IS ASSUMED TYHAT
10-4 tm3 OF SOLID WASTE IS GENERATED BY THE
REPROCESSING OF 10.7 tons OF FUEL.

 

S 1. LWR FUEL; EXPOSURE 33,000 Mwd/ton AT
30 Mw/ton
> . LWR FUEL; EXPOSURE 45,000 Mwd/ton AT
30 Mw/ton
10-5 . LMFBR FUEL (CORE + BLANKET); EXPO-
SURE 33,000 Mwd/ton AT 58 Mw/ton
5
2
1076
01 0.2 05 1 2 S 10 20 50 100 200 500 1000

TIME (years)

Fig. 5.1. Variation of Heat Generation Rate in Solid Waste with
Time After Discharge from Reactor.
*a

51

cylinders. The cylinders are 3 m long and, even when full of waste with
the highest heat-generation rate, their center line temperature must not
exceed 90000.5'lu’ 515 With these assumptions, the cylinder diameter
can be up to 28 cm if they are cooled by water or up to 21 cm if they

are cooled by air. In both cases the cylinders would be filled with
waste only for 75% of their volume. Therefore, their effective capacity
would be 138 and 78 liters, respectively. Tables 3.7 and 3.8 are tabu-
lations of some of the thermal characteristics of waste cylinders.

The initial heat-generation rates in the cylinders would be 6900
cal/sec and 3900 cal/sec according to the size. This is equivalent to
heat fluxes through the cylinder surfaces of 0.33 cal/sec/cm? and 0.25
cal/sec/cmg, respectively. If the cylinders were standing in air in an
environment at a constant temperature of 27OC, heat removal could be
achieved by natural convection and radiation with the cylinders' surface
at a temperature between 40O and 5OOOC. The heat flux by natural con-
vection from a vertical surface at 420°C to air at 2700 is about 0.09
cal/sec/cmg. For the same conditions the heat flux due to radiation from
a material with a surface emissivity of 0.5 is about 0.16 cal/sec/cme.
The sum of the fluxes is equal to the thermal flux through the surface

3.1k, 3.15

of the small cylinders. For the large cylinders a thermal
flux of 0.353 cal/sec/cm2 would be reached with a surface temperature
close to 5OOOC. Under actual storage conditions a cooling system would
be necessary for both cylinder sizes.

If a different solidification process were used, different parame-
ters would be necessary for the calculations, but the final result would
be similar. In case of granular solids produced by the fluid bed process,
several advantages and disadvantages should be considered. The advantages
are: (1) no glass-forming materials need be added; (2) the energy re-
quirements for processing are lower due to the lower temperatures needed;
(3) the final product is lighter; and (4) a greater volume reduction is
achieved. On the other hand, the disadvantages are that: (1) the final
product has a much higher leachability and (2) the product has a very low
thermal conductivity, requiring the use of smaller containers or the ex-

tension of storage in liquid form. Fluid bed solidification could result

in a reduced cost for the three steps: (1) solidification, (2) interim
Table 3.7. Thermal Conditions of Cylinders Full of Waste

with the Highest Heat Generation Rate

 

Heat Generation

 

 

Wall Center Line
Diameter Rate 3 Cooling Temperature Temperature
(cm) (cal/sec/cm”) Medium (°c) (°c)
D o
28 5 x 10 Water at 50 C 50 870
28 5 x 1077 Boiling water 100 920
21 5 x 1077 Air L20 880
Table 3.8.

Total Heat Generation Rate and Thermal Flux

in Freshly Filled Cylindersa

 

 

Volume® of Surface® of Total Heat Thermal Flux
Cylinder Cylinder Waste in Waste in Generation at the Surface
Diameter Length Cylinder Cylinder Rate of Cylinde
(cm) (cm) (cm?) (cm™) (cal/sec) (cal/sec/cm”)
28 300 138,400 21,100 6,900 3.3 x 1071
21 300 77,850 15,500 3,900 2.5 x 107+

 

“Assumes cylinders 75% full.

ce
33

storage as solid, and (3) transportation to the ultimate disposal site.

This saving would be balanced by a possible increase in risk. There would

also be an additional cost due to the longer storage period as liquid.

Similar considerations would be possible for every other solidification

process.

5.1,

5.2.

5.5,

3.4.

3.5,

3.6.

3.7.

3. 8.

3,9,

5.10.

5.5 References

A. Jouan, La vitrification en pot des solutions molybdiques de
produits de fission, SCCI-109 (1968).

K. J. Schneider, Status of Technology in the United States for
Solidification of Highly Radioactive Liquid Wastes, BNWL-820
(1968).

R. E. Commander, G. E. Lohse, D. E. Black; E. D. Cooper, Operation
of the Waste Calcining Facility with Highly Radioactive Agueous
Waste, IDO-14662 (1966).

B. E. Paige, Leachability of Glass Prepared from Highly Radioac-
tive Calcined Alumina Waste, IDO-14672 (1966).

A. M. Platt, Editor, Quarterly Progress Report, Research and

 

Development Activities, Fixation of Radioactive Residues, May,
June, July 1968, BNWL-889 (1968).
A. M. Platt, Editor, Quarterly Progress Report, Research and

 

Development Activities, Fixation of Radioactive Residues, August,
September, October 1968, BNWL-923 (1968).
R. J. Thompson, J. E. Mendel, J. H. Kleinpeter, Waste Solidifica~

 

 

tion Demonstration Program: Characterization of Nonradioactive
Samples of Solidified High-Level Waste, BNWL-1393 (1970).

A. M. Freke, "Some Aspects of the Public Health Hazard Associated
with the Storage or Disposal of Glasses Incorporating Highly Active
Fission Product Wastes," Health Phys. 12, 1077~1086 (1966).

D. W. Rhodes, Storage and Further Treatment of Product from Flu-
idizeed Bed Calcination of Radioactive Wastes, CONF-660208 (1966).
U. L. Upson, Observed Properties of Some Solidified High-Level
Wastes and Their Stability Under Simulated Storage Conditions,
CONF-660208 (1966).
5.11.

5.12.

5.13.

3.1k,

5.15.

3,16.

bl

M. N. Elliot and D. B. Auty, "The Durability of Glass for the Dis-
posal of Highly Radioactive Waste, Discussion of Method and Effect
of Leaching Conditions," Glass Technology 9(1), 5-13 (1968).

 

J. R. Grover and D. Walmsley, The Durability of Fingal Glass:
Part 3. The Effect of Heat Treatment, AERE-R5583 (1968).

 

 

ORNL Staff, Siting of Fuel Reprocessing Plants and Waste Manage-
ment Facilities, ORNL-L451 (1970).

J. O. Blomeke, Letter to W. H. McVey, U. S. Atomic Energy Commis-
sion (Feb. 26, 1969).

 

 

W. Davis, Jr., Temperature Profiles within Cylinders Containing

 

Internal Heat Sources and Materials of Temperature-Deperident Ther-

 

mal Conductivities, Description of Fast Computer Programs as Ap-'

plied to Solidified Radiocactive Wastes, ORNL-L345 (1969).

 

 

W. Davis, Jr., C. L. Fitzgerald, and H. F. Soard, Maximum Tempera-

 

ture Rise in Cylinder Containing Intermediate-Level and High-Level

Solidified Wastes, ORNL-4361 (1969).

 

 
e

55

4. INTERIM STORAGE OF SOLID WASTE

At this time no industrial facility for the interim storage of
solid waste is in existence; therefore the design and the technology of
future storage facilities are still in an undefinéd stage. Conceptual
designs and cost estimates are available for storage of solidified
wastes for periods ranging from several years to unlimited duration.
Proposals exist for storage in water-filled canals, in water-filled
basins, in air-cooled annular bins, in air-cooled concrete vaults, and
in air-cooled concrete wells.u'l’ h.2

The annular-bin concept has been developed for granular solids
produced by the fluidized bed process. These solids can be transported
pneumatically to the bins. However, this storage method does not seem
suitable for wastes that must be removed after a few years and trans-
ported to a different ultimate disposal site. Therefore, only storage
facilities for waste cylinders that can be transported without additional
processing will be considered in this report.

Most of air-cooled facilities considered assume that cooling is by
natural convection. For example, the British proposal for storing glass
prepared by the Fingal process is to use air-cooled vaults using natural
convection; the warm air escapes through a chimney, and air circulation
is maintained by the thermal gradient produced by decay heat.u'5
Such a concept has been proposed fof the final disposal of solidified
waste.u'B’ holy

This system 1s not sulitable for waste containing large amounts of
transuranics, because the integrity of the concrete vaults and chimneys
could not be guaranteed for the extremely long containment times re-
quired. Furthermore, cooling by natural convection implies that the
heat-generation rate in the waste is low. This means that a long perioa
of interim storage as liquid would be required. In our assumptions a
waste of such low heat-generation rate would be shipped directly for ul-
timate disposal in a deep geologic formation without further interim
storage on site. An air-cooled facility for the interim storage of
high-level solid waste should be suitable for waste with rather high

heat-generation rates, and therefore a forced cooling system would be

necessary.
36

With either water or air cooling, the waste would be stored in rows
of vertical cylinders. The distance between cylinders would be controlled
by the heat-generation rate of the waste and by the heat-removal capacity .
of the cooling system. An air-cooled facility, because of the smaller
diameter of the cylinders and of the lower cooling efficiency of air in .
comparison with water, would require more space to accommodate a unit
amount of waste.
For the case of under-water storage, it is believed that much tech-
nology could be common with present-day pools for the storage of irra-
diated fuel elements. Water would provide both cooling and shielding,
and the handling of cylinders would be much simpler than in an air-cooled

facility.

4.1 Routine Operation of Interim Storage Facility

In order to define the reference dimensions of the facility, we as-
sume an interim storage facility assoclated with a reprocessing plant
having a capacity of 7.5 tons/day (2250 tons/year). We further assume

that the waste is solidified by a glass-forming process and that the .

-~

solid waste has the characteristics described in the preceding chapter.

With these assumptions, the solid waste production is 210 m5 per year

in 1520 28-cm-diam waste cylinders; for an air-cooled facility serving the

same reprocessing plant, the production would be 2700 21-cm-diam cylin-

ders per year. If the storage time as solid is about 9 years, the fa-

cility must eventually have a capacity of 13,700 cylinders. If the

cylinders are arranged in parallel rows and if each cylinder is allowed

a space 1.5 times its diameter in one direction and twice its diameter

in the other, the area per cylinder of 28-cm diameter is 2350 cmg. Add-

ing to this a 25% allowance for service areas, we obtain an area of 2940

cm2 per cylinder. The total area required for 13,700 cylinders would be

4000 m2. With a depth of water of 12 m, the volume of water in the fa- ]
cility would be 48,000 m5, plus the water present in the heat exchanger )

and demineralization systems.

5 of solid -

waste which may have a total heat-generation rate from 17 x 106 cal/sec

At capacity, the storage facility can accommodate 1900 m
57

to 25 x lO6 cal/sec. Therefore, the potential thermal impact of maximum
heat rejection will be equivalent to that of a 30 to 50 MW(e) nuclear
power reactor.

With the preceding assumptions, the ratio between volume of waste
and volume of water is about 1/25, and dividing the volume of the waste

5

by the floor area of the storage facility, we obtain L7 cm” of waste for
every square centimeter of floor area. It seems likely that canals or
basins will be covered by a building and that the ventilation system will
include a condenser to recirculate the water evaporated by the decay heat.
Under operating conditions, the average temperature of the cooling water
in the facility is assumed to be about 5OOC. The facility will be de-

signed in such a way that faulty containers can be located and repaired

or reencapsulated.

4.2 Siting Considerations

If we accept the apparently reasonable assumption that the storage
facility for high-level solid waste will be located near the reprocessing
plant, eite selection will be mainly controlled by the requirements of
the fuel reprocessing plant. The problem of the siting of a fuel repro-
cessing plant has been treated in detail in the ORNL Fuel Reprocessing

Plant Siting Report.t:’

The main siting criteria will be: (1) rational
location in relation to fuel sources, (2) acceptable population distribu-
tion, (3) low seismicity, (4) availability of water, and (5) acceptable
meteorological conditions. In relation to the meteorological require-
ments, it must be noted that a reprocessing plant with the capacity of
7.5 tons per day would produce daily from 80,000 to 100,000 Ci of 85Kr,
and some system of disposal other than release to the atmosphere may be
necessary. The disposal of gaseous effluents by deep well injection or

85

the separation of ~“Kr and its shipment to a suitable disposal site as
compressed gas in gas cylinders or as dispersion in a glassy matrix would
reduce the importance of the meteorological characteristics of the gsite.
The storage facility for high-level solid waste will add little to
the site requirements. In the case of a water-cooled facility an adequate

source of cooling water would be necessary.
38

Negligible amounts of activity would be expected to be released
routinely to the environment from the storage facility. Both in a water-
cooled and in an air-cooled facility the waste would be stored at some
depth below the ground surface. The hydrologic characteristics of the
area, lncluding ion exchange capacity of the geologic materials, the rate '
and direction of groundwater movement, and regional water utilization,
would need to be investigated.u'6 For all other operations that might
result in spilling and leaking of contaminated solutions, a rather deep
water table and good ion exchange capacity of the geologic materials
are desirable features. A low permeability and high ion exchange ca-
pacity of the surrounding geologic materials would be a desirable natural
barrier to prevent widespread contamination of the environment by the
nonvolatile radionuclides and to provide time for remedial measures in

case of disaster.

4.3 Possible Mechanisms of Activity Release .
During Interim Storage -

All industrial plants present a certain risk for man; in every com- .
plex plant many accidents are possible and, therefore, many risks must be

considered. As Farmer has observed, "

there 1s no logical way of dif-
ol 7 All accident

evaluations should aim to a quantitative estimate of the probability of

ferentiating between credible and incredible accidents.

the accidental situation. One should bear in mind that the probability

of an accident will likely increase with time due to progressive wear and

deterioration of the plant. The risk associated with an accident can be

equated as the product of the probability times the consequences. For

the risk to be acceptable either the probability must be low or the con-

sequences must not be serious. If the consequences of a particular

accident are considered catastrophic, it will be the responsibility of

the engineers to design the plant with appropriate safeguards to reduce

the probability to the low level necessary to make the risk acceptable. ”
The quantitative evaluation of the probability of accidents is very dif-

ficult, especially in the nuclear industry which meritoriously has very »
insufficient statistics. However, the probabilistic approach seems to be

the only scientifically valid one for the plants of the future.
Te

59

The only accident to the storage facility with possibility of very
serious consequences is a long or permanent loss of cooling. For a design
to be considered acceptable, the probability of such accident must be
vanishingly small. As far as the loss of cooling accident is concerned,
it seems that the critical situation would be the release to the atmos-
phere of cesium and ruthenium upon melting of the waste.

The evaluation of consequences of possible accidents to the solid
waste storage facility requires assumptions about specific site conditions;
therefore, for didactic purposes, we assume a storage facility located in
the Oak Ridge Reservation in an outcrop of Conasauga shale. Since evalu-
ations of the consequences of an accident to a high-level liquid waste
tank located in a hypothetical tank farm in the same location are avail-
able, this choice will permit some useful comparisons.

For liquid waste tanks, 1t is considered that releases of activity
could be caused by one of the following: (1) tank corrosion, (2) loss of
cooling, (3) hydrogen explosion, or (L) external causes (earthquake, war-
fare, sabotage, flood, etc.).u'8 So far tank corrosion has been the only
cause of tank failures. Several tanks in the United States have developed
leaks in the course of time, and occasionally high-level waste has been
lost to the ground. For example, at Savannah River one of the tanks has
lost to the ground about 1000 gal of high-level waste with an estimated
3000 Ci of fission products.u'9 At Hanford 11 tanks have developed leaks
to date. In at least one of these cases several thousand curies of fis-
sion products have been lost into the ground.h°lo In none of these cases
have significant levels of radioactivity been observed to have migrated
far from the point of release. Still this relatively high number of tank
failures demonstrates that the probability of release of radionuclides
when wastes are stored in liquid form is finite. It is believed that the
engineers who will design a solid waste storage facility will have the
opportunity of substantially increasing the intrinsic safety of the stor-
age. bBvery high~level solid waste storage system will provide for double
containment; every primary container for solid waste (e.g., the waste
cylinder) will contain a very small fraction of the activity contained in
one liquid waste tank. Waste cylinders will be easily accessible and easy

to inspect. If we compare the possible causes of tank failure listed
Lo

above with possible causes of accidents to solid waste, it i1s evident
that in the latter case, no radiolytic hydrogen formation is possible
inside the containers; but container failure, loss of cooling, and ex-
ternal causes still must be considered.
The probability of container failure, in any kind of storage fa- s
cility, is finite. A leakage of activity from the container could be
caused by a defective sealing, by a release of overpressure bullt up
inside the container, or by an abnormally high corrosion rate. Under
normal conditions none of these events should cause any undue hazard.
The cooling fluid monitors would reveal the leakage, and remedial action
could be taken.
In case of a water-filled storage facility, the loss of cooling
can take two forms: a failure of the water circulation and cooling
system, or a loss of water. TFor the average heat-generation rate in
the storage facility, we will consider the three possible waste types
of Table 3.6. In all three cases the initial heat-generation rate is

5 »

assumed to be 5 x ]_O-2 cal/sec/cm” j about 10 years after discharge from .
the reactor the heat generation is reduced to 2.8 x 10'5, 3.8 x 10'5,
and 2.1 x 1072 cal/sec/cm5, respectively, for LWR waste (33,000 MWd/ton),

LWR waste (45,000 MWd/ton), and LMFBR waste. The average heat-generation

24

rate in the storage facility, according to the type of waste that is con-
sidered, is 9 x 1077 cal/sec/cmB, 1.2 x 107° cal/sec/cm?, or 1.1 x 10°°
cal/sec/cm5 respectively.

Theoretically, 1/25 of the average heat generated per unit volume
of waste is available per unit volume of water. With the assumed average
water temperature of SOOC before the loss of cooling, the time required
for the water to reach boiling is about 38 hr for the minimum heat-
generation rate and 29 hr for the maximum. If no water is added, in 17
and 1% more days, respectively, all the water present in the facility
would be evaporated, if the initial rate of heating is maintained. (This
is a very approximate calculation; all effects of progressive reduction
of depth of water on transmission of energy from waste to water are ne-
glected. The design of the interim storage facility will include pro-
visions for the condensation and recycling of evaporated water, and this

would prolong the time required for evaporation to dryness.) Therefore,
te

b1

after loss of cooling, if no remedial action can be taken, the water
would be heated to 100°C and eventually boiled away. On the other hand,
for as long as water covers the top of the waste cylinders, their wall
temperature will not exceed lOOOC and no damage of containers is likely.
Therefore, with waste stored in water there would be a certain amount

of time, after the occurrence of an accident, during which remedial ac-
tion could be taken to prevent extensive damage.

If no remedial action is taken or if the accident had caused open-
ings in the bottom of the canals or basins and the water were lost, the
waste cylinders would start a progressive self-heating. Such a serious
situation could only be caused by catastrophic circumstances that would
make 1t impossible to take the necessary remedial action. If we assume
that the water has been lost and that no remedial action is taken, the
heating rate of the cylinders would be controlled by their age and by the
naturally occurring heat removal mechanisms.

Several possibilities must be considered in relation to heat removal.
If the cylinders were left standing on the bottom of empty canals and
basins, there would be heat removal by radiation and by convection. If
the cylinders were to fall and lie on the bottom, the amount of heat
removed by radiation and convection would be lower. If the cylinders
were covered by the rubbish of collapsed building and canal walls, even
smaller amounts of heat would be removed by conduction, and both heating
rates and temperatures attained would be at a maximum. In this last case
some cylinders could be broken by the collapse. Because of the many
uncertainties, no quantitative assessment of the above factors has been
attempted-at this time. For cylinders in air, it seems likely that only
containers full of waste with a very high heat-generation rate could
reach the melting point of stainless steel. If cylinders were buried
by a collapsed building, many more would melt. For cylinders that do
not melt, but are heated to substantial temperatures, it would be neces-
sary to evaluate the consequences of the overheating, in relation to in-
creased corrosion, and internal pressure buildup.

If a container fails, the volatile components of the waste could be
released to the atmosphere from the molten waste. Because of their rela-

tively low vapor pressures, most of the released activity would be due
L2

to cesium and ruthenium. Cesium could be released from molten waste at

a rate of 0.5 to 1% per hour.u'll The release of ruthenium is difficult i
to assess; the available data indicate a rather erratic behavior. Oc- .
casionally, ruthenium release rates as high as the ones for cesium have -
been observed.u'll In Table 4.1 are shown the amounts of lO6Ru, 15403, ‘
and 157Cs that could be released to the atmosphere in a time of the order

of 100 to 200 hr after each cylinder melted.
If we assume that only cylinders that have been in storage less than

1 year will release activity to the atmosphere, we can calculate that in

lO6Ru, 5 X lO7 Ci of lBqu, and 2 x 108
¢i of 7¢s could be released in case of LMFBR waste, and 6 x lO8Ci of

lO6Ru, 5 x 108 Ci of lBqu, and 2 x 108 Ci of 157

a few days as much as lO9 Ci of

Cs in case of LWR waste
(exposure, 33,000 MWd/ton). Releases of this order of magnitude could
have catastrophic consequences.
If a similar accident should occur in an air-cooled concrete vault,
the accident would evolve faster because of the absence of any water to
evaporate. It is likely also that, because of the smaller waste cylin- ;
ders and the greater distance between them, the atmospheric release would
be somewhat less. In both kinds of storage facilities, however, the non- °
volatile components of the waste would remain in situ and be subjected
to quite different events. At the high temperatures reached in the
storage facility, the concrete would decompose and eventually the waste
would come into contact with the surrounding geologic materials. In this
condition waste might be exposed to leaching by water and radionuclides
transported through the ground. At this point two possibilities must be
considered. If the waste is below the water table, groundwater would
seep towards the waste continuously. If the waste is above the water
table, only rainwater falling directly on it or percolating through the
ground would reach it. In the case of waste above the water table, as-
suming that the yearly rainfall is 1330 mm and that rainwater falls di-
rectly on the waste, with 47 cm5 of waste for each square centimeter of
rain collecting floor area, the average heat production in the waste suf- -
ficient to evaporate the rainfall completely is 5.3 x 1077 cal/sec/cmB.
We can see in Fig. 3.1 that waste will exceed this heat-generation rate .

for a considerable length of time. Considering that the rainfall is not
Table 4.1. Inventory of Volatile Radionuclides in Freshly Filled Cylinders
(curies)

 

106 134

Ru 157

Cs Cs

 

Pf-cm diam® 2l-cm diam® 28-cm dian® Pl-cm diam® 28-cm diam® 2l-cm diam’

 

LMFBR

waste® 1.2 x 106 7.0 x lO5 4.0 x lOLL 2.2 X lOL‘L 1.5 x lO5 8.0 x lOu
LWR

wasted 6.1 x lO5 5¢5 X lO5 2.5 x 105 1.h x lO5 1.5 x ]_O5 8.0 x lOLL
LWR

waste® 6.9 x 10° 3.7 x 10° 3.4 x 10° 1.9 x 10° 2.0 x 10° 1.1 x 10°

e

 

aOne cylinder contains waste from 1.5 ton of fuel.

bOne cylinder contains waste from 0.8 ton of fuel.

“Fuel (core and blanket) exposure, 33,000 MWd/ton; 58 MW/ton.
Upuel exposure, 33,000 MWd/ton; 30 MW/ton.

®Fuel exposure, 45,000 MWd/ton; 30 MW/ton.
L

. uniformly distributed throughout the year, it is more meaningful to cal-
culate the amount of water that might fall on the waste during a very
high intensity storm. Let us assume a storm with a total precipitation
of LOO mm in 24 hr. Although this would be an exceptional event, an

5 5

average heat-production rate of 6 x 10~ cal/sec/cm” could furnish enough
energy to evaporate this amount of water in 24 hr. Therefore, the down-
ward transport of activity by percolating rainwater would be prevented
or substantially reduced for rather long times.

In case of waste located below the water table, the amount of ground-
water that could come in contact with the waste would be controlled by
the seepage rate through the shale and the area through which the seepage
occurs. Assuming a seepage rate of 2 cmE/cmg/day and a seepage area of

5

of waste (based on the geometry of the storage canal),

L 5

cal/sec/cm” would be enough to

1 cm2 for 110 cm
an average heat production of 1.3 x 10~
completely evaporate all the groundwater seeping into the storage area.
If we assume that seepage into the canal occurs from all directions and
that the average thickness of seepage is 7 m (average depth of water

5

of waste. Under

5

table, 5 m), we obtain 1 cm2 of seepage area for 50 cm
these conditions, an average heat production of 3 x 10'” cal/sec/cm
would be required to evaporate the incoming groundwater.

Even 1f the shale were able to produce this flow of water towards
the waste, all water would be evaporated for several decades. Only after
the heat-production rate has decreased enough to allow some water to seep
back into the formation after having been in contact with the waste would
the transport of activity by groundwater begin.

Loss of volatile radionuclides to the atmosphere in the first phases
of the accident would reduce the heat-production rate. This heat-
generation reduction is limited to something between 4 and 139 of the
total heat-generating capacity, depending on the type of waste, and would
not change the above considerations significantly.

In conclusion, the loss of cooling might result in the melting of
a fraction of the waste cylinders and in the atmospheric release of the
volatile components 1f remedial action is not taken. At high temperature
the concrete of the bottom of canals, basins, or vaults would be decom-

posed. The water reaching the waste would be evaporated for a fairly
L5

long time but eventually would leach activity out of the waste and trans-

port it through the ground.

h.h Movement of Radionuclides Through the Ground

For the transport of radionuclides through the ground, it is assumed
that the earth behaves like a large unidimensional ion exchange column.
No lateral or vertical migration or dispersion is considered, but the
spread of the solute is assumed to occur in the same manner as described
by Glueckauf for the elution of a band of solute through a chromatographic
column.u'lg This gives rise to conservative estimates of migration and
levels of soil loading, because multidimensional movement or dispersion
would result in greater amounts of soil material being contacted within
a given linear distance. The details of the assumptions and calculations
can be found in Appendix A and are based on information obtained in pub-
lished literature wherever possible.

The results of some typical calculations for the extent of movement

Mgy, 270s, 25%py, ana 2h

of ;Am from a variety of physical forms of

’
stored wastes are depicted in Figs. 4.1 to L.4. 1In all cases it is as-
sumed that rno remedial action is taken to deter underground movement.

The rates of movement of all radionuclides are considerably lower than
that of the transporting solution, due to the absorptive properties of
soil material. One interesting aspect of these calculations is that they
indicate that the original physical form of the waste material 1s of
limited importance in restricting the long-term radionuclide movement.

The reasons are: (1) Even for the relatively insoluble solidified wastes
the times reguired for dissolution are shorter than those required for
radioactive decay of the long-lived radionuclides. Thus, a large fraction
of the total activity of long-lived radionuclides would be dissolved if
the waste were exposed to the leaching action of groundwater. (2) Most
anions do not interact strongly with mineral surfaces; so the increased
electrolyte content of groundwater, due to liquid leaks or to dissolution
of the more soluble solid material, would be dissipated more quickly than
the pulse of radioactivity released. This means that for most of the time

the pulse of radiocactivity would be transported in groundwater of normal
O
ol

o—b

SOIL LOADING (uCi/g)
S 3
! 1
o -

<
w

10~ 7

Fig. L.1.

Material.

L6

ORNL—DWG 71-9711

 

 

 

 

 

 

 

 

 

 

 

™\
0.27y
T\ N\100y
B
\ \ 200 vy
L
T o

 

 

 

 

\
\ 600 y\
\

\\ 400 y
\

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

\ \
Voo
N\
AN
N
0 50 100 150 200 250
DISTANCE MIGRATED (m)
. 90
Predicted Movement of

Sr from the Leaching of Pot Calcine
L7

ORNL-DWG 71-9712

10~1

10~3

SOIL LOADING (xCi/g)

1075

 

10~7
0 10 20 30 40 50 60 70
DISTANCE MIGRATED (m)

157

Fig. L.2. Predicted Movement of Cs from the Leaching of Spray

Melt Material.
L8

ORNL-DWG 74-9713

 

O—L

 

 

(uCisq)

 

10

|
//3
~
O
~<

 

 

 

200,000 y
V <IN

 

SOIL LOADING
O
|
O
| nmanmameet
\

el N S e

 

N\ 400,000 y

 

 

 

 

 

 

 

\
1077 / /\

 

 

NN

 

 

O 200 400 600 800

1000

DISTANCE MIGRATED (m)

239

Fig. 4.3. Predicted Movement of
a

1200

1400

Pu from the Leaching of Glass
Leach Rate Controlled by Diffusion of 1079 cm?/sec.
t

SOIL LOADING (uCi/g)

L9

ORNL-DWG 71—-9714

 

10!
10~
10~
10~°
000y
10~7
0 500 1000 1500 2000 2500 3000

DISTANCE MIGRATED (m)

2kh1

Fig. 4.4k. Predicted Movement of Am from tge Leaching of Glass

2

Having a Leach Rate Controlled by Diffusion of 107~ cm /sec.
50

concentrations rather than in a highly salted solution and that the rates

of radionuclide migration and extents of movement would be essentially

the same regardless of the initial salt concentration. In the case of .

157Cs, selective adsorption limits its movement very markedly. This 1is -

due primarily to the steric favorability of exchange sites on most clay #’
h.13, 4. 14

minerals for ions the size of cesium. Field measurements of the
extent of cesium movement in Conasauga shale due to liquid releases into

surface pits confirm that cesium mobility in this formation 1s quite
4L.15
low.

157

Strontium-90 would be expected to be somewhat more mobile than Cs,

especially in cases where caustic is not added to favor coprecipitation
with calcium carbonate.u'l6 Strontium would be expected to behave simi-
larly to calcium, which is the predominant stable element on the exchange
complex of most soils in temperate climates.

Plutonium-239, plutonium-240, americium-241, and americium-243% would

15705 or 9OSr,

be expected to migrate considerably further than either
primarily because of their much longer half-lives. Ewven though the rates

of movement of these nuclides are very low due to formation of radiocol-

loids, there can be appreciable translocation if leaching is continued
for thousands of years. These extents of movement are based on the prop-
erties of Conasauga shale. ©Shales generally have very good sorptive
properties for radiocations because of their high clay content and rela-
tively slow rates of water migration due to their low permeability. Other
formations may restrict the migration of radionuclides to a much lesser
extent, 1f the waste is subjected to the leaching action of moving ground-
water. If the formation is devoid of water, migration could occur only as
the result of surface diffusion on earth particles; migration in systems
where there 1s water that is rnot moving could occur as surface diffusion
and molecular diffusion in the interstices of the formation. 1In these
cases one would expect the rates of migration to be orders of magnitude
less than in situations where convective transport by moving groundwater
occurs. ¢
Actually, under the local conditions in Conasauga shale, the trans-
porting groundwater would intercept the surface after moving about 60 m. .

In this situation the initial mobility of the waste has a marked influence
51

on both the concentration and total quantity of radionuclides that reach
surface waters (Figs. 4.5 to 4.8). This is especially true for 13703
which has both a very restricted rate of movement in the ground and a

short half-life relative to the transuranics 259Pu, 2LLOPu, 24lAm, and

216Am.

Of course 1t is impossible to ascertain that a given direction and
rate of groundwater flow will be maintained for thousands of years, but
if the assumed conditions are continuously maintained, significant migra-
tion of each of these radionuclides could occur before they had decayed
to innocuous levels. During such time periods, it may also be an over-
simplification to assume that the solid matrix on which absorption occurs
is not moving. Hence, it should be pointed out that the calculated ex-
tents of movement of these radionuclides are subject to large degrees of
error and that the results are not to be construed as real predictions
but are to be used only as an indication of the relative extent of move-

ment that could be encountered.

4.5 Conclusions

It is believed that a loss of cooling accident could develop into
the very serious situation described if no remedial action were taken in
time. The lack of remedial action could be caused only by an external
major disturbance that at the same time causes the loss of cooling and
prevents further operation of the storage facility. Such an external
cause can be imagined as natural or caused by human action. In case of
natural disasters, such as earthquakes and floods, both the probability
and the consequences of an accident would be minimized by careful design
and siting.

The evaluation of the probability of man-caused disruption, either
because of madness, sabotage, or warfare, cannot be based on characteris-
tics of the site and will not be discussed here. However, appropriate
siting of the facility and suitable geologic conditions at the site would

always minimize the gravity of the consequences.
52

ORNL-DWG 74-9715

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o' T T T T T T T T
o T T
Q | : LIQUID RELEASE (10%gal TANK)
o | Ll L
x 40 1]
7 /E T
’ Lol |
1072 I I . HE
o | CrTer T !;‘ LEACH FROM POT CALCINE
z I o OO T
< 03 8 OO O O S S LEACH FROM
W 10 T T T IR SPRAY MELT PRODUCT]
LT AT T
] ‘ P | | ]
% 107 by ] . H
o IR 1T /’ LEACH FROM GLASS F
% L 1 | ‘ 4 (107° cme/sec)
= 1 . ; ; ; ol
I LA AT T T
X i [ LEACH FROM GLASS
: }‘] | ‘/ (10"6cm2/sec)
> . - -
5 10-6 / ;*I | ! K #‘
- | | 1
2 i i
= N y [i |
2 o7 L lf L 1 | |
107! 10° 10* 102 103 104
TIME (years)
9

Fig. 4.5. Cumulative Fraction of OSr Originally Present in Various
Forms of Waste That Would Reach a Seep 60 Meters from the Source Under
Conditions of Continuous Leaching.

¢
‘e

55

ORNL-DWG 71-9716

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o
© T T T
4 } e
I | R
£ 4o LIQUID RELEASE (10° gl TANK)
3 | o
ul | 1 |
E 402 ’ L |
© 10 1f / f'l; "
Z e L
Q L e L
g 10 e
s .0 Jl't .1, NOTE THAT WHEN RELATIVELY STABLE SOLIDS ARE
5 o4 oo ' FORMED THE MIGRATION OF '37Cs IS DELAYED
L T ~ ENOUGH TO ALLOW IT TO DECAY BEFORE IT CAN |||
. | Pt
> | / | REACH THE SURFACE.
o o i Do .o .
cos bl L - g
2 il e [ | |
& g | |
| |
S 106 o R e |
5 T
4 : ol | P |
D N l!; ‘ ol ;
% 10°7 L] Lo Lo !
© 107! 100 10! 102 103 104
TIME {years)
157

Fig. 4.6. Cumulative Fraction of Cs Originally Present in Various
Forms of Waste That Would Reach a Seep 60 Meters from the Source Under Con-
ditions of Continuous Leaching.
Sk

ORNL-DWG 74-9747

 

I
I {

 

0
o 10
T T T

[

LIQUID RELEASE f
(108 gal TANK)

 

 

 

 

N\

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3
n
\\
\\
S
\ s TN
N\
\‘
\

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L

Q

&

@

D

w

w

I

—

O

Z

5

< 1

& / / A

g 1073 /

= /

: ] / [y

L yo-4 ] 1! LEACH FROM S /

s POT CALCINE / /LEACH FROM GLASS
-4 A | AR

g 1073

& S T T /! | l I

i | / ' LEACH FROM | & | nn

> | " sPRAY MELT propucTt| | [ 1] s

kz 1076 / — ' - f | L

< / ! ; . | ' !
3 ' i | i Pl ‘
2 o | {] 1! ) ol

3 // | NI / ]3] |

010-7 Ll i 1 il , L |

10'1 100 101 102 103 104

TIME (years)

Fig. 4.7. Cumulative Fraction of 2LLlAm Originally Present in Various
Forms of Waste That Would Reach a Seep 60 Meters from the Source Under Con-
ditions of Continuous Leaching.
ORNL-DWG 71-9748

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

100
o
: yd
(I ”‘—'
3 107 7
: /
= /
g 1072 /
T
Q
3 /1
@ 40-3 /
]
g / /
3 /
N
w 10-4 } + b } i /
o LIQUID RELEASE (108 gal TANK) ]
& e ] m 1 j LEACH FROM GLASS
5 o5 L/ LEACH FROM POT CALCINEJ /(106 ¢ /nec) |
<L P | o
& LEACH FROM SPRAY
W MELT PRODUCT
g 10° / ISLEACH FROM
= GLASS (1073 cmz/sec)
b
3 107 | L L
100 10! 102 103 104 103

TIME (years)

. . . 2 o . .
Fig. 4.8. Cumulative Fraction of 59Pu Originally Present in Various
Forms of Waste That Would Reach a Seep 60 Meters from the Source Under Con-
ditions of Continuous Leaching.
L. 10.

L.11l.

4.12.

56

h.6 References

J. J. Perona, R. L. Bradshaw, and J. O. Blomeke, Comparative
Cost for Final Disposal of Radioactive Solids in Concrete Vaults,
Granite, and Salt Formations, ORNL-TM-664 (1963).

J. O. Blomeke, J. J. Perona, H. O. Weeren, and R. L. Bradshaw,

 

 

Evaluation of Ultimate Disposal Methods for Liguid and Solid
Radioactive Wastes: Part III. Interim Storage of Solidified
Wastes, ORNL-3355 (1963).

D. W. Clelland, A. D. W. Corbet, and R. F. Coles, "Design of a

 

Plant for the Incorporation of Highly Active Wastes Into Glass,"
Chem. Engr. Progr. Symp. Ser. 65(9%), 89-101 (1969).
L. C. Watson, H. K. Roe, R. W. Durham, E. J. Evans, and D. H.

 

Charlesworth, Methods of Storage of Solids Containing Fission

Products, CRCE-736 (June 1958).

 

ORNL Staff, Siting of Fuel Reprocessing Plants and Waste Manage-
ment Facilities, ORNL-L451 (1970).

 

F. Gera, 0. Ilari, M. Mirone, C. Sennis, and F. Veloné, Guida per
la raccolta delle informazioni necessarie per l'analisi e la
valutazione del sito di un reattore nucleare, PROT SAN/06/69,
CNEN, Ttaly (1969).

F. R. Farmer, "Reactor Safety and Siting: A Proposed Risk Cri-
terion," Nuclear Safety 2(6), 539-548 (1967).

J. 0. Blomeke and L. C. Emerson, A Safety Analysis of Tank Stor-
age, ORNL-TM-1465 (1965), pp. 35-k41.

J. Henry Horton, Jr., Savannah River Laboratory, Aiken, South

 

Carolina, personal communication, 1969.
D. J. Brown, Atlantic Richfield Hanford Company, Richland, Wash-
ington, personal communication, 1969.

A. E. Albrethsen, L. C. Schwendiman, Volatilization of Fission

 

Products from High Level Ceramic Wastes, BNWL-338 (1967).
E. Glueckauf, "Theory of Chromatography. Part 9. The 'Theoreti-

1"

cal Plate' Concept in Column Separations,

35-LL (1955).

 

Trans. Faraday Soc. 51,
L.13.

b, 1k,

h.15.

L.16.

57

D. G. Jacobs, "Sorption of Cesium by Conasauga Shale," Health
Phys. 4, 157-163 (1960).
D. G. Jacobs and T. Tamura, "The Mechanism of Ion Fixation Using

"

Radioisotope Techniques,” Trans. 7th Int. Congr. Soil Sci., Madi-
son, Wisconsin 2, 206-21k (1960).

T. F. Lomenick, D. G. Jacobs, and E. G. Struxness, "The Behavior
of Strontium-90 and Cesium-137 in Seepage Pits at ORNL, Health
Phys. 13, 897-905 (1967).

D. G. Jacobs, "Ion Exchange in the Deep Well Disposal of Radio-
active Wastes," pp. 43-54 in Int. Collog. on Retention and Mi-

gration of Radioactive Tons in Soils, Saclay, France, October 16-

18, 1962 (1963).
58

5. GEOLOGIC PROCESSES RELEVANT TO THE ULTIMATE DISPOSAL

Early proposals for long-term management of high-level radioactive
waste apparently assumed that a thousand years containment would be suf-
ficient. However, we believe that, in view of the projections of Chap-
ter 1, much longer containment times will be required because of the
presence of transuranics. A realistic evaluation needs to be made of
the long~term hazards that would result from the presence of plutonium
isotopes in the environment. At present it seems prudent to assume that
the hazards are high and that the waste will require containment for
periods of several hundreds of thousands of years, which is very long
relative to man's written history of a few thousand years. The only
realistic solution to such a problem is utilization of a relatively deep
geologic formation which, by its nature, is capable of permanently pre-
venting the waste from entering the bilosphere. The selection of a suit-
able formation will require the capability of making some kind of geologic
predictions for the time period covering the next million years.

It is necessary to consider such factors as change in climate, change
in hydrology, erosion (channel and hillslope erosion, glacial erosion,
etc.}, tectonism (orogeny, epeirogeny, subsidence, etc.), and volcanism,.
Al]l these need to be evaluated in addition to the short-term geological
considerations of faulting, earthquakes, groundwater motion, etc., that
are normally considered in the siting of nuclear facilities.

Geology, up to the present time, has been a science with limited
predictive capability. ©So far no consistent, comprehensive theory capable
of explaining the major geologic features of the earth has been available.
Developments of the last few years may eventually provide earth scientists
with a logical model capable of explaining the tectonic features of the
earth. The recent demonstration of ocean floor spreading has caused the
rebirth and affirmation of the once-dead theory of continental drift.

From this recent evidence has evolved a new tectonic interpretation called

5.1-5.5

plate tectonics. The new theory is presently based mainly on
oceanic data. In the future a careful reevaluation of the geologic in-
terpretation of continental areas will be necessary. The question to be

answered is if the detailed knowledge of continental geclogy can be
59

reinterpreted in agreement with the moving plates of a dynamic earth.
If plate tectonics theory survives this test, geologic predictions should
become feasible.

The particular kind of predictions necessary for management of radio-
active waste are concerned with small areas and relatively short periods
of time, geologically speaking. Therefore to have predictions of practi-
cal utility in relation to the waste management problem, fine details
for local areas will need to be included in the general model. While it
seems reasonable that eventually this will become possible, it is pres-
ently impossible to estimate how long it will take.

At this time, it is impossible to make exact predictions, but we can
evaluate upper limits for the order of magnitude of geologic changes ex-
pected in the next few hundred thousand years. Such evaluations are based
on two kinds of observations:

1. The present rate of geologic processes.

2. The magnitude of changes that have occurred in the recent

geologic past.

For the second point a study is required of selected geologic events
of the Quaternary period. Unfortunately, cursory review of the literature
about Quaternary geology brings to light many difficulties: 1like a con-
fusing terminology and duration estimates for this period varying from

5.4-5.9

700,000 years to more than 3 million years. Such disagreement is
hard to believe for this best known of all geologic periods, but it is

a fact that many correlations between geographically separated Quaternary
successions are controversial. The problem is'complicated by boundaries
based on stratigraphic features that are generally time transgres-

5.10-5.12 In addition most Quaternary successions do not contain

sive.
rocks suitable for radioactive dating. However, we can conservatively
assume that events reported as having occurred during the Pleistocene or

the Quaternary¥* evolved in a time span of about a million years.

 

*The Quaternary period includes two epochs: Pleistocene and Holo-
cene. The Holocene began 11,000 years ago; therefore its duration is
negligible in comparison with the rest of the Quaternary.
60

A million years is not a very long time from a geologic point of
view. All major geological features of the earth required much longer
times for their evolution. Still, it is known that during the Pleisto-
cene the earth's crust was subjected to local changes of great magnitude.
There is evidence that we are living in a geologically peculiar period.
Characterized by fast changes, typical, at most, of only a few earlier

5.15

time spans of comparable length. For the past 90 million years the
epicontinental seas have been retreating and the average elevation of
continents has been increasing, resulting in an extreme condition of
continentality. This causes severe climatic conditions and high rates
of erosion and sedimentation,” o~2* ¥
In the Pleistocene, wide areas have been uplifted while others have
been covered with hundreds of meters of sediments, proof of fast sub-
sidence. The climate has been subjected to a series of major changes
that have resulted in repeated glacial episodes. Mean sea level has
been rising and falling according to the amount of water bound on land
as ice. Rivers have cut deep valleys and then refilled them with sedi=-
ments only to cut again into the sediment. Several erosion cycles have
occurred, as shown by the remains of terraces along many valleys. Gla-
ciers have left a typical morphology in wide areas with steep glacial
valleys, lakes, moraines, drumlins, and eskers. The melting of the ice
caps removed a load from areas of the earth crust that had previously
subsided under the weight. The isostatic uplift in these previously
glaciated areas has been and is, in a geological sense, a very fast
movement. The last maximum in the extent of glaciation was only 20,000
years B.P. (before present); since that time the sea level has risen

5.15

more than 100 m. Other geological phenomena that are able to change
the physical condition of certain areas in times that are short even

compared to historic times are faulting and volcanic activity.

5.1 Stream Erosion

Rates of erosion vary greatly from place to place, and in the same

place from time to time. The rate of denudation (the average rate at
1 ®

61

which material is removed from an area) is controlled by climate, relief,
and the lithological nature of materials subjected to erosion; occasion-
ally, human activity is a major factor. In Table 5.1 are listed some
examples of long-term denudation rates for a few geographical regions.

In Table 5.2 are estimates of ‘present regional erosion rates for several
geographical regions of the United States.

The effect of agriculture and other human activities on the rate of
denudation can be quite pronounced. Judson has estimated the present
rates of erosion in west-central Italy, especially north of Rome, and
compared them with the denudation rates before the days of agricul-

ture.S'go

The present rates of erosion, determined from stream records,
agree very well with archaeological records extending over more than

2000 years. In Table 5.3 are shown some rates of erosion for archae-
ological sites near Rome. It is interesting to observe that most of the
sites mentioned in the table are located in hilly areas with an eleva-
tion of a few hundred meters above sea level. The historical rates of
erosion vary between 10 and 100 cm/1000 years with most of the data in

the range of 20 to 50 cm/lOOO years. For the preagricultural era,

erosion rates of 2 to 3 cm/1000 years are indicated, about an order of
magnitude less than in historical times. It is likely that in the future,
with the present trend in population increase, human pressure on the en-
vironment will increase.5'20’ 0-21

Ursic and Dendy have studied the annual sediment yields from small
upland watersheds in northern Mississippi. The production of sediments
is greatest from cultivated land and is lowest for pine plantations and
mature pine-hardwoods; intermediate values are observed for pasture,
abandoned fields, and depleted hardwoods.5'22 Table 5.4 shows the
values; the range is striking, covering more than three orders of
magnitude.

Table 5.5 illustrates the influence of relief and climate on de-
rudation. Denudation rates for plateaus and high-elevation piedmonts,
areas which are high above sea level but which have slopes similar to
those of lowlands, are intermediate between those of the mountains and
the lowlands. Areas of very recent orogenesis will have the steepest

5.23

relief and the highest denudation rates.
 

 

 

Table 5.1. Past and Present Rates of Denudation
(from Menard, 19615'16)
DéziZed Time” Dzoii?is benud- Ratlo of
5 5 £ p6 3 ation Past Rate Present Rate Past and
Region (107 ®¥m™) (10" yr) (107 km”) (km) (em/1000 yr) (em/1000 yr) Present Rate
. d
Appalachian 1.0 125 7.8 7.8 6.2 1.1 5.6
Mississippi 3,0 150 11.1 6.9 h.6 L. 6° 1.0
b
(1.6)
Himalaya 1.0 40 8.5 8.5 21 100" 0.2
Rocky Mounta%n 0.8 25 0.6 0.7 3 ——- -—-
(L. Cret.)
Rocky Mountain < 0.4 40 2.0 > 4.8 12 - 20 -—- ——-
(U. Cret.)
aGeological Names Committee, 1958, U. S. Geological Survey.
bArea denuded in past.
Gilluly (1949).°" 7
dSuspended load of rivers + 33% (33% added by Leopold et al., l96h).5'18
®Suspended load of rivers + 109 (10% added by Leopold et al., 196&).5'18
fSuspended load of rivers.

<9
Table 5.2.

Rates of Regional Erosion in the United States

(Modified from Judson and Ritter, l96h5'19)

 

Drainage

Load (tons/kmg/yr)

 

 

_ Aread Runoff . Average
Drainage 5 o 5 2 Denudation 9% Area  Years of
Region (107 km~) (l0” m”/sec) Dissolved Solid Total (cm/1000 yr) Sampled Record
Colorado 629 0.6 23 417 e 17 56 30
Pacific Slopes, 303 2.5 36 209 245 9 Ll I
California
Western Gulf 829 1.6 b1 101 142 9 9
Mississippi 3238 17.5 39 N 133 5 99 12
South Atlantic 736 9.2 61 48 109 L 19 7
and Eastern
Gulft
North Atlantic 383 5.9 57 69 126 5 10
Columbia 679 9.8 57 Ll 101 L 39 < 2
Totals 6797 46.9 b3 119 162 6

 

a .
Great Basin,

St. Lawrence, and Hudson Bay dralnage not considered.

¢9
Table 5.35. Rates of Erosion Based on Data from Archeological Sites Near Rome ™

(Modified from Judson, 19685'20)

 

 

Erosion
Archeologic Length Nature of Slope Rate
Site of Record Measurement Bedrock (degrees) (cm/1000 yr)
Veili 800-600 B.C. Erosion over graves Pleistocene 3-7 30
to present in Villanovan tuff
Cemetery
Villa Formello A.D. 0-100 Exposed footings Pliocene sand L 50
to present of cistern and gravel
Exposed footings Pliocene sand 7
of mausoleum and gravel
Casentile A.D. 100-200 Exposed footings Pleistocene 'l 50
to present of cistern tuff
Casalacia A.D. 0 to Exposed footings Pleistocene T 30
present of cistern tuff
Sambuco 200-100 B.C. Movement of Miocene clay 7 ' 40
to present foundations and lime-
stone
Via Prenestina 500-100 B.C. Exposed footings Pleistocene '’ 50
to present of road tuff
Treia 1000-450 B.C. Sediment accumu- Pliocene clay 2-90 100
lated from and gravel--
known area Pleistocene
tuff

 

aDepth of erosion is based on a density of 2.6 for the material eroded.

9
Table 5.4. Sediment and Surface Water Yields®

 

 

 

(Modified from Ursic and Dendy, 19655‘22)
Average Average ‘Annual Sediment Yields Denudation Ratesb
Annual Annual
Land Use or Rainfall  Runoff Means Ranges Means Ranges
Cover Type (mm) (mm) (tons/hectare) (tons/hectare) (em/1000 yr) (cm/1000 yr)
Open land:
Cultivated 1320 405 48 7.35-96.50 185 28-371
Pasture (one unit) 1295 380 3.61 2.67-4.55 1L 10- 17
Forest land:
Abandoned fields 1295 180 0.29 0.023-1.21 1.1 0.1-5
Depleted hardwoods 1295 130 0.23 © 0.045-0.72 0.9 0.2-3
Pine plantations 1570 25 0.045 0.00-0. 18 0.2 0.0-0.7
Mature pine hardwoodsC 1295 250 0.045 0.02%-0.09 0.2 0.1-0.3%
cullies®® 1345 408 189-895 1570 727-3442

 

®Data are means of 9 values, 3 replications of each cover for the 3 years, 1959-1961, except pine
hardwoods (1960-1961).

Prssumes a density of 2.6 for material eroded.
“These watersheds are on hydrologically shallow soils.
QAverage annual rainfall and sediment outflow from seven gullies for the 5 years, 1956-1960.

°c. R. Miller, Woodburn, Russel, and H. R. Turner, "Upland Gully Sediment Production,” Symposium
of Bari, Internatl. Assoc. Sci. Hydrol. Pub. 59, 1962.

 

59
66

Table 5.5. Relative Rates of Denudation in Uplands and Lowlands
in Different Climates

(Modified from Corbel, 19595-25)

 

Estimated Rate
of Denudation
Physiographic Environment (em/1000 yr)

 

Lowlands: slope = 0.001
Periglacial climate, permafrost 1.5
Climate with snow accumulation in winter

Temperate oceanic climate (Lower Rhine, Seine,
Lower Loire)

Continental climate (Missouri-Mississippi)
Hot-dry climate (Mediterranean-New Mexico)
Tropical desertic climate (Central Sahara)

Hot-moist climate with dry season

N W O WU
N Do~ N
—~
9
~—

Hot-moist climate, equatorial

Mountains: slope 2 0.01

Periglacial climate (Glamaa, Bdvra, Ht. Drac, Arve) 60
Extreme nival climate (Southeastern Alaska) 80
Oceanic climate, intermediate elevation 22
Mediterranean climate, high elevation b5

(Durance, Gran Sasso)

Mediterranean climate, semi-dry 10
(Isonzo, Brenta)

Hot-dry climate (Southwestern United States, 18
Tunisia)

Hot-moist climate (Usumacinta) 9.2

 

)
67

Schumm, by plotting the denudation rates for drainage areas of about
4000 km2 versus the relative relief of the basin (relief of basin divided

5.24

by basin length), obtained the curves of Fig. 5.1. Curve 1 is ob-

tained by plotting calculated maximum values, while curve 2 represents

5.4

average rates of denudation. Curve 2 has been obtained by extrapolat-
ing the rates of denudation actually observed in small basins located in
the semiarid Western United States. The extrapolation to erosion rates
for drainage basins of 4000 km? is based on a relation between drainage

5.25

area and rate of erosion proposed by Brune. According to this rela-
tion, rates of denudation are inversely proportional to the 0.15 power of
the drainage area. Because length is constant, Fig. 5.1 shows also the
increase in denudation rates as the relief of the basin is increased to
9000 m‘5.2h-5.28

Most of the denudation rates mentioned above are average values for
entire basins or even for large-scale geographical regions. It should be
kept in mind that erosion can be very much more active on a local scale.
A small drainage basin in the loess hills of Iowa, with an area of 3.k
kmg, provides an extreme example. Here sediments are being removed at a
rate which produces a denudation for the basin of 12.8 m per 1000
years.5'29 Loess is characterized by little resistence to erosion;
therefore after all the loess is removed, the rate of erosion will be
expected to decrease.

The rate of valley cutting by streams can be very different from
the average rate of denudation of an entire watershed. A classic example
of this is the Crand Canyon. The plateau which has been carved by the
Colorado River extends over much of Utah, Arizona, New Mexico, and
western Colorado. The morphology of the plateau surface indicates a
very advanced erosion cycle. The region formed a peneplane when it was
uplifted to a height of 1800 to 2400 m above sea level; this started the
present erosion cycle, during which the Canyon was carved. The Grand
Canyon is a very impressive morphologic feature, 350 km long and with a
maximum depth exceeding 1600 m. The time required for the formation of
the Canyon is difficult to assess, but estimates of 1.5 to 2 million
years are probably close to the truth. This gi&es an apparent cutting

rate of about 80 cm/lOOO years for the Canyon, almost five times -as high
68

 

 

 

 

 

 

 

   

N
»
ORNL-DWG 69-7028
RELIEF-LENGTH RATIO
0 002 004 0.06 008 0.4
400 l | | I l

E 1

O

L300 et 2 ]

O

O

o

\\

&

Q

~ 200 B 4

zZ

9 |

}_

=

S )\

Z 100

0O
*

/
O |

 

 

 

 

 

0 3000 6000 9000
RELIEF (meters)

Fig. 5.1. Relation of Denudation Rates to Relief-Length Ratio and
Drainage Basin Relief. Denudation rates are adjusted to drainage areas of
about 4000 km®. Curve 1 is based on the average maximum denudation rate
of 91.5 cm/lOOO years when relief-length ratio is 0.05. Curve 2 is based
on actual data from small drainage basins in areas underlain by sandstone
and shale in semiarid regions of the western United States (Modified from
Schumm, 19635.24),
69

>»as the regional denudation rate, 17 cm/lOOO years, estimated by Judson
and Ritter.5'19 The real cutting rate could be even higher, because the
Colorado River has cut the present depth of the Canyon plus the thickness
of material removed from the surrounding highlands. Not many rivers

can be expected to have deepened their wvalleys at such a high rate, but
many valleys show evidence of changes in floor level in Quaternary times

5.30-5.53

of hundreds of meters.

5.2 Orogenic and Epeirogenic Uplift

The Colorado Plateau is a very good example of how a peneplane with
very low erosion rates can be rejuvenated and subjected to much higher
erosion rates. Consideration of possible erosion rates of the future
must not overlook the possible uplift of the area.

The Table 5.6 is a partial list of areas that have been subjected
to uplifting in Pleistocene times. Some of these rates of uplift are
rather high. For example, the foothills of the southern Himalaya have
been uplifted about 1800 m since the beginning of middle Pleistocene.

In Calabria (southern Italy) early Pleistocene marine sediments have been
found at an elevation of 1000 m above sea level. However, these values,
if averaged, give minimum rates, because the major portion of the uplift
probably occurred during a fraction of the total time. In fact, rates

of uplift measured at the present time in areas of active orogeny far
exceed the average values obtained from geologic evidence. In Table 5.7
are some examples of present rates of orogenic uplift. The rates of
epeirogenic uplift observed by Cailleux along seacoasts are much lower.
The average value is 1 mm/year, with a range between 0.1 and k4

5.3k

Kafri reports observations about vertical movements in

5.55

mm/year.
northern Israel. From these data it can be concluded that velocity

of movement is very time dependent. For intervals of a few years, dis-

placement rates as high as 50 to 60 mm/year were observed. On the other
hand, for time intervals of about 20 years the velocities are a few

5.35, 5.36

millimeters per year.
10

 

 

Table 5.6. Partial List of Highlands Uplifted in Pleistocene Time
(Modified from Flint,® 1957°°1%)
Type of Uplift
E = epeirogeny Amplitude
Highland Unit 0 = orogeny (meters) Date
Americas
Rocky Mountains, Colo. E 1800 Post-late Pliocene
San Juan Mountains, E 1000 Post-late Pliocene
Colo.
Uinta Mountains, Utah E 24 00-3000 Pliocene and Early
Pleistocene
Rocky Mountains, Mont. E Many hun- Late Pliocene and Early
dreds of Pleistocene
meters
Basin and Range region, E Early Pleistocene
Nevada, etc.
Sierra Nevada, Calif. E 600 Early Pleistocene
Coast Ranges, Calif. 0 Mid-Pleistocene or later
Coast Ranges, Alaska 0 1500 Pleistocene
East Greenland E Pleistocene
Iceland E Pleistocene
Venezuela Cordillera E Pleistocene
Andes, Peru E 1600 Pleistocene
Andes, Bolivia E 1500 Pliocene and Pleistocene
Europe
Scandinavian Peninsula E Pleistocene
Alps E 2000 Pliocene to mid-
Pleistocene
Apennines 0,E 1000 Pleistocene
Dinaric Alps E Early Pleistocene
Asia
Caucasus Mountains E 800~1200 Pleistocene ,
Pamir Mountains E Late Pliocene and
Pleistocene
Tien Shan E Late Pliocene and
Pleistocene
Himalaya Mountains E 1800 Post mid-Pleistocene
Mountain ranges in E Many hun- Pliocene or Pleistocene
Yunnan, China dreds of
meters
Mountain ranges in E,O Pleistocene
Siberia
Oceania
New Zealand Alps E,O 2000-3500 Culmination: late
Pliocene and Early
Pleistocene

 

%F1int (1957), pp. 501-502.
71

Table 5.7. Some Present Rates of Uplift
(Data from Schumm, 19655'2u)

 

Present Rate of Uplift

 

Location (mm/yr) Source

San Antonio Peak, Calif. 5.2 Gilluly (1949)
Buena Vista Hills, Calif. 12.8 Gilluly (19:9)
Cajon Station, Calif. 6.1 Gilluly (1949)
Baldwin Hills, Calif. 8.8 Gilluly (1949)
Alamitos Plain, Calif. 4.9 Gilluly (1949)
Santa Monica Mountains, Calif. 4.0 Stone (1961)
San Jose Hills, Calif. 4.0 Stone (1961)
San Gabriel Mountains, Calif. 6.1 Stone (1961)

Japan, average L.6 Tsuboi (1933)

Japan, range 7.6 - 0.8 Tsuboi (1933)
Persian Gulf 10 Lees (1955)
Persian Gulf 3 Lees (1955)

 

5.5 Glacial Erosion

The high average elevation of the continents in late Cenozoic time
and the widespread highlands have been one of the causes of the large

5.k, 5.13 The morphology of very

areal extent of Pleistocene glaciers.
wide areas of the earth has been shaped by glaciers, which are very active
geomorphic agents. The amount of denudation in glaciated areas due to

the action of glaciers is difficult to evaluate. The available data

show, however, that the rate of denudation has been quite variable.S'15

The rate of glacial erosion is controlled by several factors: (1)

rate of glacier movement, (2) thickness of ice, (3) amount and physical
character of the drift which constitutes the base of the glacier, (ki)
erodibility of the geological materials beneath the glacier, and (5) to-
pography. The glacial deposits left in Germany, Poland, and Russia con-

tain very large volumes of rocks of Scandinavian origin. There is no
72

doubt that the Scandinavian mountains have been subjected to extreme
rates of erosion. The Sogne Fjord in Norway has been eroded for a total
apparent depth of 2400 m if we consider the valley depth both above and
below sea level. TFjords are very likely the most impressive morphologic
features produced by glacial erosion. In Table 5.8 are listed the deep-
est known fjords. The great depth of many fjords could be due in part
to stream erosion during the interglacial periods, but it definitely

appears that ice has been the main geomorphic agent.

Table 5.8. Greatest Known Fjord Depths

(Modified from Flint, 19575‘15; originally in Peacock, 19357)

 

 

Geographical Deptfib
Location (m) Name
British Columbia 780 Finlayson Channel
Alaska 878 Chatham Strait
(outer part)
Norway 1210 Sogne Fjord
Patagonia 1288 Messier Channel

 

“Flint (1957), p. 97; originally in M. A. Peacock,
"Fjord-land of British Columbia,'" Geol. Soc. Am. Bull. 46,
633-696 (1935).

bValues given are depths of water; depths to bedrock may
be greater.

 

It is believed that the large valleys of British Columbia and
southern Alaska have been deepened by glaciers by at least 600 m. At the
present rate of erosion (2000 cm/1000 years) the Muir Glacier in southern
Alaska would remove 600 m of rock in about 30,000 years.s'15 Very high
rates of erosion have been recently observed by Washburn in eastern Green-
land, where the seasonal freeze and thaw in a nearly glacial climate
causes denudation rates ranging between 900 and 3700 cm per 1000

5.5

years. In Table 5.9 are some examples of present rates of glacial

5.23

erosion taken from Corbel. According to Corbel glacial erosion is,
on the average, four times more effective than fluvial erosion. If only
the maximum erosion rates are considered, we find that the rates due to

glacial erosion are 25 times the rates due to torrential erosion.
75

Table 5.9. Present Rates of Glacial Erosion

 

 

(Data from Corbe15'25)

Name of Name of Geographical Denudation
Torrent Glacier Location (em/1000 yr)
Dranse Valais, France 100
Bossons Chamonix, France 180
Nant Blanc Etendard French Alps 160
Heilstruga Norway 140
Memurelven Norway 160
Auserfjbtur Iceland 220
Jokullsd Iceland 220
HoffelsjBkull Iceland 320
HofsjBkull TIceland 180
Isortok Western Greenland 250
Saskatchewan Canada 200

Muir™ Alaska 500

Hiddenb Alaska 5000

 

aThe rate of erosion mentioned by Flint for this glacier is
four times higher.

bThis extremely high rate of erosion is related to a period
of very rapid advance at the beginning of this century. The front
of Hidden glacier advanced about 3 km at the rate of 10 to 15 m
per day. During this period, the glacier produced 30,000,000 m5
of sediments.

Many lakes in North America and in Europe occupy valleys and basins
that have been excavated and deepened by glaciers. Many glaclal basins,
presently occupied by lakes, have their bottoms several hundreds of meters
below sea level. The troughs of the Finger Lakes in central New York
were excavated to the present depth of 450 to 600 m below the tops of
adjacent highlands by a combination of stream and glacier erosion. The
Hudson River Valley between Newburgh and Peekskill, New York, has a bed-

rock floor that is between 200 and 300 m below sea level. The eastern
Th

part of the basin occupied by the Great Slave Lake has a floor more than
600 m below the lake surface.”"

At the same time it is known that very wide areas subjected to gla-
ciation have been denuded at a very low rate. An example of a very re-
duced rate of glacial erosion can be seen in the Canadian Shield,
particularly in the Flin Flon district, LOO miles southwest of Hudson
Bay. Here the glaciers failed to erase the preglacial morphology, and
it is believed that the total denudation did not exceed a few meters.
Undoubtedly, the effectiveness of glacial erosion has varied extensively
with geographic location. Glacial erosion differs considerably from
stream erosion, and it deserves careful consideration, not only because
of the very high rates that it can possibly attain, but also for its
capacity to extend the erosive action many hundreds of meters below sea

level.

5.%5.1 Cause of Glaciation

 

Glacial periods are exceptional events in the geologic history of
the earth. Many possible causes have been proposed to explain the recur-
rent ice ages. The most likely explanation is that glaciations are
caused by a concurrence of circumstances. Probably the main cause is
related to a suitable distribution of oceans and lands. In order for
glaciers to extend, the geographical position of the poles must permit
growth of large ice caps, and continents at high latitude must have a
high average elevation. Once these general conditions are met, the in-
dividual glacial periods are probably triggered by insolation variations,
with a mechanism first proposed by Milankovitch and later supported by
many other authors. The importance of insolation variations seems to
be proved by the correspondence between the minimums in the insolation
curve and the minimum temperatures in ocean waters estimated from the
180/160 ratio in the carbonate of shells of pelagic Foraminifera. ™2
If this interpretation is correct, a new glacial period can be expected
in about 10,000 years, when an insolation minimum will again occur. At
that time the northern areas that have been covered by ice during the
last glacial maximum will have completed their isostatic recovery and

5- 38‘50)-‘-1

will have an average elevation higher than at present.
te

75

5.5.2 Uplift of Previously Glaciated Areas

 

The isostatic uplift of previously glaciated areas is of such mag-
nitude as to compensate not only for the weight of removed ice but also
for the weight of material eroded. Fenno-Scandia is the best known ex-
ample of such a movement. The area has been uplifted in a dome-1like
shape with the maximum recovery in the region of the Gulf of Bothnia,
where the ice had attained the maximum thickness. Estimates as high as
1500 m have been made for the total recovery, but it is likely that the
uplift has not been quite so great, probably not more than 500 to 600 m.
However, such a large uplift in a time span of less than 20,000 years
would drastically affect the whole erosion pattern of any region. The
present rate of uplift is still nearly 1 cm/year in the north of the
Gulf of Bothnia; Fairbridge has calculated that around 10,000 to 11,000

5.38 It has been

B.P. the rate of crustal uplift was at least 10 cm/year.
estimated that the isostatic uplift still to be expected in the area is
about 210 m. 2" 12 The glaciated areas of North America are known to have
been subjected to a dome-like uplift very much like Fenno-Scandia. Un-
fortunately, the available knowledge of the postglacial recovery of North
America is not so complete as for the Baltic area. The rate of tilting
seems to be about 1 mm/100 km/year, which is less than in Fenno-Scandia.
It has been estimated that the center of the dome in the Hudson Bay region
can be expected to rise another 260 m. In the Hudson Bay area, post-
glacial marine sediments have been found at altitudes of about 270 m.5'8
It is known also that much of the northwestern coast of North America
has been uplifted in postglacial time. Near Vancouver, postglacial marine
sediments have been found up to 230 m above sea level. In Alaska similar
sediments have been reported up to 180 m above sea level.

As might be expected, uplift has been reported also for all the
other areas known to have been glaciated, such as the British Islands,
Iceland, Spitsbergen, Novaya Zemlya, Siberia, Greenland, Patagonia, and
the Antarctic. Among these areas, the highest uplift has been observed
in Greenland, where postglacial marine sediments have been found up to

200 m above sea level. Measurements made in northeastern Greenland sug-

gest a present rate of uplift of 1 cm/year.
76

During the maximum ice extension, the sea level was 150 to 150 m
lower than its present level; eustatic changes in sea level, naturally,

affect the rate of erosion of areas where the sea is the base level.

5.4 Subsidence

So far we have considered uplift and erosion as possible causes of
drastic changes of the physical conditions of geologic formations. The
possible effect of subsidence and the related high rate of sedimentation
should be considered also. The main result of this phenomenon is a
shifting to greater depth of the whole stratigraphic column, with the
consequent changes in temperature and pressure.

Temperature and pressure are conditions of concern for the ultimate
disposal of radioactive wastes regardless of the nature of the disposal
formation. However, in case of disposal in salt formations, because the
plasticity of salt increases markedly with temperature, there is concern
that elevated temperatures might affect the stability of the formation.
Consideration of this factor has led to a reasonable limitation that the
temperature in a disposal facility in salt should not exceed EOOOC;
higher temperature could conceivably be tolerated in rock formations
less subject to plastic deformation, but the temperature would still
need to be limited. 1In areas of normal geothermal gradient (lOC every

30 to 35 m), a temperature of EOOOC would be reached at a depth of about

6000 m. There are many areas where the geothermal gradient is much higher

(up to lOC every 10 to 15 m) and where QOOOC would be expected at shal-
lower depth. In a hole drilled for oil in California, a temperature of
2O5OC was measured at the depth of about 4900 m. In a well drilled in
Texas, the bottom hole temperature at the depth of 7280 m was more than
2710(3.5'MB In Table 5.10 are examples of geothermal gradients measured
in the United States.

Besides deep burial in the earth crust, high temperature of a geo-
logic formation can be caused by the nearby intrusion of igneous masses.
Rather high temperatures can be caused also by exothermic chemical reac-
tions; for example, in oil-bearing formations, and by radioactive decay

in formations rich in radioactive elements.

e
e

TT

 

 

" Table 5.10. Geothermal Gradients at Selected Localities in the United States
(Modified from S. P. Clark, Jr., Editor, 19665'“”)
Station
Elevation Thermsal Number of
Above Geothermal Conductivity Heat Flow Values
Sea Level Gradient (103 cal/ (10-6 cal/ Averaged Year of
Locality (m) (OC/km) cm. sec. C° cm~.sec) Together Publication
Grass Valley, 667 9.2 6.0 0.6 1 1957
Calif.
Bakersfield, 207 35.0 3.7 1.29 1 1947
Calif.
Regan County, Tex. 700 8.3 13.0 1.1 12 1956
Eddy County, N. M. 700 8.5 12.6 1.1 5 1956
Lea County, N. M. 1000 9.2 13.0 1.2 (?) 1 1956
Colorado Springs, 1885 20 7.0 1.4 (2) 1 1947
Colo.
Griffin, Lagrange, 300 4.3 7.0 1.0 (2) 2 1963
Ga.
Front Range, Colo. 2500 22 7.8 1.7 1 1950
San Manuel, Ariz. 970 15 8.0 1.2 (?) 1 1948
Calumet, Mich. 360 18.6 5.0 0.93 1 1954
Butler, Pa. 200 29 3.8 1.2 (?) 1 1960
Doddridge, W. Va. 200 29 4.2 1.4 (2) 2 1960
Marion, W. Va. 200 3Y 3.5 1.20 (2) 1 1960
Harrison, W. Va. 200 37 3.k 1.26 (?) 1 1960
Oak Ridge, Tenn. 340 12 6.1 0.73 1 1963
Washington, D. C. 30 15.7 7.1 1.12 1 1964
Boss, Mo. 375 17 7.6 1.29 1 1963
Bourbon, Mo. 290 15 8.1 1.22 1 1963
Delaware, Mich. 389 16 5.3 0.95 1 1963
White Pine, Mich. 281 16 6.7 1.07 3 1963
Metaline, Wash. 686 20 11.6 2.31 L 1963
Gov't Canyon, Utah 1860 40 4.7 1.9 1 1963
Eureka, Utah 1702 80 L.k 3.51 (?) 1 1963
Yerington, Nevada 1034 27 8.7 2.3%6 3 1963
Barstow, Calif. 1245 2l 8.8 2.1 2 1963
Alberta, Va. 116 18 7.8 1.4 1 1965
Aiken, S. C. 100 15 6.7 1.0 6 1965
Salt Valley, Utah 1500 38.5 3.4 1.2 5 1964

 
78 ’

The following examples indicate the order of magnitude of rapid
Quaternary subsidence. Since early Pleistocene times the Colorado River
has accumulated more than 900 m of sediments on the southwestern tip of
Arizona. The Gulf of California embayment has subsided many hundreds
of meters in Quaternary times. In the Gulf of Mexico, the thickness of
Pleistocene sediments increases as one moves away from the coast. It
has been calculated that near the outer edge of the continental shelf
the Pleistocene sediments must be approximately 3000 m thick. The Snake
River Plain is located in the southern part of Idaho; in this area the
Quaternary features have very large dimensions (for example, the Quater-
nary section is about 1500 m thick). The area is characterized by very
intense Quaternary volcanic activity, and basalt makes up much of the
total thickness of Quaternary rocks.

The Great Valley of California is an elongated subsidence basin that
has accumulated sediments since mid-Cretaceous time. In the area of maxi-
mum thickness the post mid-Cretaceous sequence is approximately 12,000 m
thick. In the southern half of the Great Valley, Cenozoic sediments reach
exceptional thickness; and in the south end of the San Joaquin Valley,
there are 4500 m of continental sediments accumulated since late Pliocene
or early Pleistocene time. Very thick Quaternary sediments can be found
also in the Ventura and Los Angeles Basins of southern California. This
is one of the thickest marine Quaternary sections in the world. The lower
Pleistocene alone can be as thick as 1500 to 1850 m.

However, considering that the most likely depth of disposal in salt
formations will be between 300 and 800 m and that a subsidence of several
thousand meters would be necessary to increase the formation temperature
to excessive values, it seems that such an event could not possibly occur
in a time period of a few hundred thousand years. Similar considerations
for disposal into other formations are not possible at this time, because
little consideration has been given to the temperature and depth limita-
tions. The heating caused by the decay heat generated in the waste would
only affect a limited area of the salt formation and, from a geologic
point of view, would be of such short duration that no consequences would
be expected. In fact it has been calculated that in a few thousand years

the temperature in the disposal formation would be back to normal.S'L‘L5
79

5.5 Volcanism

Another geologic phenomenon that should be investigated in relation
to the selection of a geologic formation for the ultimate disposal of
radioactive waste 1s volcanism. This phenomenon is discussed briefly

in Chapter 6 (pages 89-91).

5.6 Faulting

It is generally believed that large earthquakes are caused by fault-
ing or movement along fault planes. Faulting is the sudden fracture of
layers of the earth's crust when the accumulated strain exceeds the com-
petence of the rocks. This sudden disturbance can affect the surface
morphology through regional warping, tilting, rift formation, cracking
of the ground, triggering of landslides, modification of drainage, and so
on. Besides these surface effects, faulting can drastically change the
groundwater circulation pattern. Emergence of water, in the form of
springs, through the crushed rock of the fault zone i1s common along many
faults; occasionally the water is hot.S'u6 It is clear that the possi-
bility of faulting must be carefully considered in the evaluation of a
waste disposal site. At the present stage of geological knowledge there
is no area of the earth for which the possibility of faulting can be ab-
solutely excluded. Of course, faulting is especially intense along the
mobile belts of the earth, but even for stable mid-continental areas
without records of seismic activity the probability of faulting cannot
be considered equal to zero.

Faults are known in all possible dimensions, from very small frac-
tures with displacements measured in centimeters to huge fractures with
continental dimensions. The San Andreas fault in California is one of
the best known examples of large faults; it can be followed almost con-
tinuously for about 1000 km. The displacement is mainly horizontal. The
best estimates indicate a total right-lateral slip of about 400 km with

270 km since early Miocene.5'u7

5.48

about 4 cm per year.

The present average rate of movement is
80

An even larger and more impressive fault system is found in the
Rift Valleys of East Africa. This huge fault system extends for a
length of many thousand kilometers. Along these faults are located
the great African volcanoes. According to the theories of plate tec-
tonics, the African Rift Valley is similar to the rift present along
the axis of the Mid-Atlantic ridge; supposedly, the Rift Valley is the
initial fracture of a plate and later spreading will cause the ocean to

5.2, 5.3, 5.49, 5.51

invade it.

5.7 Hydrology

The possibility of groundwater reaching the waste and transport-
ing activity into the biosphere must be evaluated with the maximum care.
Naturally, at the time of disposal of the waste, there will be no cir-
culation of groundwater in the disposal formation. But either rapid or
slow geologic processes might produce undesirable changes in the ground-
water circulation. Erosion, uplift, faulting, volcanic activity, and
climatic change might all cause groundwater to reach the waste.

In the case of rock salt and other highly soluble geologic materials,
special care should be given to possible consequences of the interaction
with groundwater. Possible dissolution rates should be evaluated. 1In
areas with humid climate no salt is found at shallow depth because of
the dissolving action of groundwater. Several German salt diapirs are
topped by flat dissolution surfaces. Across the top of most shallow salt
diapirs is a mantle, with a typical mineralogic composition, called cap
rock. Normally, the thickness of cap rock decreases with depth, but it
5.52

has been found associated with diapirs more than 3000 m deep. The
average thickness of cap rock on shallow diapirs is around 100 m, but

in places more than 500 m have been penetrated by some wells. The main
constituent of cap rock is granular anhydrite that normally grades up-
ward into gypsum and calcite with such accessory minerals as sulfur and |
barite. It is now generally agreed that anhydrite in cap rock is an
accumulation of insoluble residues previously dispersed in the mass of

salt which has been dissolved and removed by groundwater. Gypsum, sul-

fur, and other minerals are produced by the alteration of anhydrite.
81

The calcium carbonate of the occasional cap rock limestone may be de-
rived from oxidation of hydrocarbons. It is clear that cap rock is
formed by the dissolution of a layer of salt far exceeding in thickness

the cap rock itself.

5.8 Conclusions

The above considerations do not exhaust the geological aspects
that must be considered in evaluating the waste-disposal problem; they
only serve to point out the possibility of marked changes in a geologic
formation in a time span of several hundred thousand years.5°55 The
evaluation of a geologic formation from the point of view of long-term
stability can be improved with better understanding of mechanisms re-
sponsible for large-scale motions in the earth. If the hoped-for de-
velopment of recent discoveries will furnish a successful explanation
of world tectonics, it is reasonable to expect that the understanding
of local phenomena and small-scale motions will follow the unvelling of

5.5k

the general picture. The same considerations apply to the problem
of future climate. No serious predictions are possible until the edu-
cated guesses of today are substituted by actual knowledge of the causes

of previous glacilations.

5.9 References

5.1. J. Tuzo Wilson, V. V. Veloussov, ''Debate About the Earth," Geo-
times 13(13), 10-22 (1968).
5.2. W. Jason Morgan, '"Rises, Trenches, Great Faults, and Crustal

Blocks," J. of Geophys. Res. 73, 1959-1982 (1968).

 

5.3. Xavier Le Pichon, "Sea-Floor Spreading and Continental Drift," J.

of Geophys. Res. 73, 3661-3697 (1968).

 

5.4. C. Emiliani, "Pleistocene Temperatures," J. Geol. 63, 538-578
(1955).

5,5. C. Emiliani, "Temperature and Age Analysis of Deep-Sea Cores,"

Science 125, 38%-387 (1957).
82

5.6. C. Emiliani, "Cenozoic Climatic Changes as Indicated by the Strati-
graphy and Chronology of Deep-Sea Cores of Globigerina-Ooze Facies,"
Annals New York Academy of Sciences 95, 521-536 (1961).

5.7. C. Emiliani, "Paleotemperature Analysis of the Caribbean Cores

A254-BR-C and CP-28," Geol. Soc. America Bull. 75, 129-1hl (1964).

 

 

5.8. D. B. Ericson, "Pleistocene Climatic Record in Some Deep-Sea Sedi-
ment Cores," Annals New York Academy of Sciences 95, 129-14h (1964).

5.9. D. B. Ericson, M. Ewing, and G. Wollin, "The Pleistocene Epoch in
Deep-Sea Sediments," Science 146, 723-732 (196k).

5.10. R. B. Morrison, '"Means of Time-Stratigraphic Division and Long-

Distance Correlation of Quaternary Successions,' Proceedings VII

 

Congress International Association for Quaternary Research, Vol. 8,

 

pp. 1-113, University of Utah Press, Salt Lake City, 1968.

5.11. C. Emiliani, "The Plio-Pleistocene Boundary,'" Science &22, 410
(1967).

5.12. C. Emiliani, "The Pleistocene Epoch and the Evolution of Man,"
Current Anthropology 9(1), 27-L7 (1968).

5.13. R. ¥. Flint, Glacial and Pleistocene Geology, John Wiley & Sons,
Inc., New York, 1957.

 

 

5.14. C. Emiliani, "The Temperature Decrease of Surface Sea-Water in

High Latitudes and of Abyssal-hadal Water in Open Oceanic Basins

 

During the Past 75 Million Years,' Deep-Sea Research‘é, hh-147
(1961).

5.15. W. L. Donn, W. R. Farrand, and M. Ewing, "Pleistocene Ice Volume
and Sea Level Lowering,' Journal of Geology ZQ(Q), 206-214 (1962).

 

5.16. H. W. Menard, "Some Rates of Regional Erosion," Journal of Geology
69, 15k-161 (1961).

 

5.17. J. Gilluly, "The Distribution of Mountain Building in Geologic
Time," Geol. Soc. Am. Bull. 60, 561-590 (1949).

 

5.18. L. B. Leopold, M. C. Wolman, and J. P. Miller, Fluvial Processes

 

in Geomorphology, W. H. Freman & Co., San Francisco and London,
196k4.

5.19. S. Judson and D. F. Ritter, "Rates of Regional Denudation in the
United States,'" J. Geophys. Res. 22, 3395-3401 (196L4).

 

 
5.20.

5.21.

5.22.

5.28.

83

S. Judson, "Erosion Rates Near Rome, Italy," Science igg, 1l -
1hh6 (1968).

I. Douglas, '"Man, Vegetation and the Sediment Yields of Rivers,"
Nature 215, 925-928 (1967).

S. J. Ursic and F. E. Dendy, "Sediment Yields from Small Water-
sheds Under Various Land Uses and Forest Covers,' Proceedings

of the Federal Inter-Agency Sedimentation Conference, 1963, U. S.

 

Department of Agriculture, Miscellaneous Publications 970, pp.
L7-52, 1965.

J. Corbel, "Vitesse de 1'Erosion," Zeitschrift flilr Geomorphologie
3, 1-28 (1959).

S. A. Schumm, "The Disparity Between Present Rates of Denudation

and Orogeny," USGS Professional Paper L5L-H, pp. H1-H13, 1963.

 

 

G. Brune, "Rates of Sediment Production in Midwestern United
States," Soil Conservation Service, TP-65, p. 40O, 1948.
W. B. Langbein and S. A. Schumm, "Yields of Sediment in Relation

 

to Mean Annual Precipitation," Transactions, American Geophysical

Union 39(6), 1076-1084 (1958).

 

A. G. Eardley, "Rates of Denudation as Measured by Bristlecone
Pines, Cedar Breaks, Utah," Utah Geological and Mineralogical

Survey Special Studies 21, 13 (1967).

 

 

R. B. Dole and H. Stabler, "Denudation," USGS Water Supply Paper
234, pp. 78-93 (1909).
S. Judson, "Erosion of the Land, or What's Happening to our Con-

tinents?", American Scientist 56(4), 356-37h (1968).

 

 

F. Fournier, Climat et Erosion, Presses Universitaires de France,
1960.

R. Moberly, Jr., "Rates of Denudation in Hawaii," J. Geol. Zi(B),
571-375 (1963).

E. D. Goldberg and J. J. Griffin, "Sedimentation Rates and Miner-
alogy in the South Atlantic," J. Geophys. Res. 22(20), 1293-L309
(1964 ).

J. N. Holeman, "The Sediment Yield of Major Rivers of the World,"
Water Resources Res. i(h), 737-747 (1968).

 

 

 
. 3k,

. 35.

.36,

.37,

. 38.

. 39.

.40,

1.

L2,

A3,

Iy

L5,
L6,

8k

A. Cailleux, "Recentes variations du niveau des mers et des

terres," Geol. Soc. France, Bull. 6(2), 135-1hk (1952).

 

U. Kafri, "Recent Crustal Movements in Northern Israel," J. Geo-
phys. Res. Th, hok6-4258 (1969).

V. A. Mattskova, "A Revised Velocity Map of Recent Vertical Crus-
tal Movements in the Western Half of the European USSR and Some
Remarks on the Period of These Movements,' in Recent Crustal
Movements, edited by I. P. Gerasimov and others, 1963. (Trans-
lated from Russian Program for Scientific Translations, Jerusalem,
1967.)

H. L. Washburn, "Instrumental Observations of Mass Wasting in the
Mesters-Vig District, Northeast Greenland,'" Meddelelser om
Groenland iéé(“>’ 1-296 (1967).

R. W. Fairbridge, "Convergence of Evidence on Climatic Change and

Ice Ages," Annals New York Academy of Sciences 95, 542-579 (1961).

 

M. Ewing and W. L. Donn, "A Theory of Ice Ages,'" Science 123, 1061-
1066 (1956).

M. Ewing and W. L. Donn, "A Theory of Ice Ages, II," Science 127,
1159-1162 (1958).

W. S. Broecker, "Absolute Dating and the Astronomical Theory of
Glaciation," Science 151, 299-30k (1966).

'

C. Emiliani and J. Geiss, "On Glaciations and Their Causes,'

Geologische Rundschau 56, 576-601 (1959).

 

W. C. Gussow, "Salt Diapirism; Importance of Temperature, and

Energy Source of Emplacement," in Diapirism and Diapirs, Memoir

 

No. 8, pp. 16-52, American Association of Petroleum Geologists,
1968.
S. P. Clark, Jr., Editor, Handbook of Physical Constants, Section

 

22, p. 488, pfiblished by the Geological Society of America, Inc.,
1966.
R. L. Bradshaw, ORNL-personal communication, 1970.

P. F. Richter, Elementary Seismology, W. H. Freeman & Co., San

 

Francisco and London, 1958.
5.47.

5.48.

5.49.

5.50.

5.51.

5.52.

5.53.

5- 51".

85

G. A. Rusnak, R. L. Fisher, and F. P. Shepard, "Bathymetry and
Faults of Gulf of California," Marine Geology of the Gulf of

 

California, Memoir 3, pp. 59-75, American Association of Petroleum
Geologists, Tulsa, Oklahoma, 196L.

L. C. Pakiser, J. P. Eaton, J. H. Healy, and C. B. Raleigh, "Earth-
quake Prediction and Control," Science 166, 1467-147h (1969).

H. W. Menard, Marine Geology of the Pacific, McGraw-Hill, New

York, 196k.

J. C. Maxwell, "Continental Drift and a Dynamic Earth," Am. Scien-
tist 56(1),

J. Tuzo Wilson, "A New Class of Faults and Their Bearing on Con-

tinental Drift," Nature 207, 343-347 (1965).

 

M. T. Halbouty, Salt Domes, Gulf Region, United States and Mexico,
Gulf Publishing Company, 1967.
T. F. Lomenick, Geological Considerations on the Burial of High-

Level Waste in Rock Salt, memorandum to E. G. Struxness et al.,

 

Oak Ridge National Laboratory, February 4, 1969.
L. Knopoff, "The Upper Mantle of the Earth,'" Science 163, 1277-
1287 (1969).

5.10 Bibliography

Dury, Editor, Essays in Geomorphology, American Elsevier, New York,

 

1966.

. Fairbridge, The Encyclopedia of Geomorphology, Reinhold, New York,
1968.

. King, The Morphology of the Earth, Oliver and Boyd, Edinburgh and
London, 1967.

. Thornbury, Regional Geomorphology of the United States, John Wiley
& Sons, Inc., New York, 1965.

 

 

C. Vita~Finzi, The Mediterranean Valleys, Cambridge University Press, New

H. E.

F. E.

 

York, 1969.

Wright, Jr., and D. G. Frey, Editors, The Quaternary of the United

 

States, Princeton University Press, Princeton, New Jersey, 1965.

Zeuner, The Pleistocene Period, Hutchinson, London, 1959.

 
86

6. POSSIBLE RELEASE MECHANISMS AFTER DISPOSAL
IN THE GEOLOGIC FORMATION

For the analysis of possible release mechanisms affecting the long-
term safety of disposal of high-level radioactive wastes, it is assumed
that the disposal formation will be at a depth of about 300 m or greater
and that all communications with the surface will have been sealed. With
these assumptions, the number of possible events which could result in
activity from the waste reaching the biosphere is very limited. They can
be classified into two general groups: catastrophic events and slow

processes.

6.1 Catastrophic Events

Two catastrophic events capable of releasing activity from the
buried waste will be considered. These are (1) impact of a large meteor-
ite at the disposal site, resulting in cratering to the depth of disposal;
and (2) initiation of volcanic activity at the site of disposal.

Detonation of a nuclear weapon at the site of disposal or acciden-
tal drilling through the disposal formation are not geologic processes

and are not considered here.

6.1.1 Meteoritic Impact

 

An estimate of the probability of impact of a giant meteorite at the
site of disposal is possible. A necessary assumption is that the fall of
meteorites is a random process and that all sites on earth have the same
probability of being hit. This 1is not strictly true because of a latitude
effect, but 1t 1s certainly acceptable as a first a'p‘proximatio.n.6'l Only
meteorites capable of cratering to a depth of at least 200-300 m are con-
sidered to be dangerous to the waste disposal facility. In this range of
depth, craters have a diameter about three times the depth.6°2 The depth
of the crater is measured from the height of the surrounding plain to the
bottom of the "crushing zone." The crushing zone is formed by allogenic

breccia; that is, by shattered rock fragments completely dissociated from

their original position. Therefore the threshold crater is a little
87

smaller than Barringer Crater, Arizona, which has a diameter of 1250 m.
According to Innes, the energy released by the impact at Barringer Crater
has been between 9 and 10 x lO22 ergs, equlvalent to about 2.3 megatons

of TNT.6'2 If the impacting meteorite had a wvelocity of 20 km/sec, it

7

must have had a mass of 4.7 x 10' kg. Using the curve of the relation-

ship between meteorite energy and crater diameter,a we obtain, for a

crater of 1000-m diameter, a required energy equal to about 4 x 1022

7 kg (assuming V = 20

ergs (= 1 megaton) and a meteorite mass of 2 x 10
km/sec).

The frequency of impact on earth of large meteorites can be evalu-
ated from consideration of two lines of evidence: observation of meteor-
ite falls and analysis of fossil impact craters. The analysis of
available data about meteorite falls and finds suggests that the fre-
quency of falls is inversely proportional to the meteorite mass. This
doesn't hold for small meteorites that are slowed by friction in the at-
mosphere and do not reach the ground in recognizable form. Several em-
pirical relations between frequency of falls and mass of meteorites have

6.3-6.5

been proposed. Of course, the resulting curves must be extrapo-

7

lated considerably to reach the range of masses of the order of 10 kg.

According to Hawkins' relation, the frequency of impacts between the

7

earth and meteorites of mass 2 x 10 kg or larger should be about
lO_lg/kmg/year. From this value of the impact probability it follows
that in the last million years about 500 impacts with meteorites exceed-

ing 2 x 107

kg should have occurred. About one-fourth of the impacts
should have occurred on land.

The second line of approach is the statistical analysis of impact
craters, or astroblemes. However, erosion is so active on earth that
only very recent craters can be recognized as definitely meteoritic. 1In
a few geologic regions, where the basement rocks are exposed, large
astroblemes of great age are recognizable. The Canadian Shield is the
region where the most extensive search for astroblemes has been conducted,
and, therefore, all estimates of frequency of impact with large meteor-
ites are based on the Canadian craters.

Hartmann has studied the problem and concluded that all craters with

a diameter greater than 10 km and formed in the last two billion years

 

®Reference 6.2, page 22%7.
88

should be recognizable, if no orogeny has affected the area in later
time (these considerations are valid only for the Canadian Shield).6'6
To convert from the number of craters larger than 10 km to the number of
craters larger than 1 km, Hartmann utilizes the relation between number
of craters and diameter size observed for lunar craters. The relation
is

Ny =K 2k | (6.1)

where ND is the number of craters with diameter larger than D and X is

a constant. Therefore

=

L . (10/1)2'LL ~ 250.

10

=

For every crater with a diameter larger than 10 km, there are about 250
craters with diameters greater than 1 km.

In conclusion, Hartmann's estimate of the frequency of impacts re-
sulting in craters with diameter larger than 1 km ranges between 0.8 and
17 x lO_lB/kmg/year. On the other hand, only three or four impact craters
with diameter greater than 1 km formed on land in the last million years

6.7,6.8

are kKnown. Possibly several craters of Pleistocene age have not
been discovered yet or have been destroyed by erosion, but the total num-
ber can hardly have been much greater than ten. With a total accessible
land surface of about 130 x lO6 km2 and ten craters in a million years,
the resulting frequency of impact is 0.8 x 10_15/km2/year. Therefore,
Hawkins' relation seems to give an overestimate of the frequency of impact
with large meteorites. On the other hand, Hartmann's range of values
seems quite realistic. Considering that meteorites are destroyed by the
impact and that, therefore, the availability of bodies for cosmic colli-
sions must have been decreasing throughout most of the life of the solar
system, the lower of Hartmann's values should approach more the frequency
of Pleistocene impacts.

If one accepts the relation expressed in Eq. (6.1) the probability
of' occurrence of craters with greater or smaller depth can be estimated.

For example, a 200-m-deep crater on top of a 300-m-deep waste repository
89

could result in leaching of waste by groundwater. The probability of
formation of a 200-m-deep crater is about five times higher than that of
a 500-m crater. If the repository were deeper than 300 m, the critical
impact would be larger and the probability of occurrence would be pro-
portionally lower. An impact capable of cratering to the depth of dis-
posal would have consequences much more serious than if the crater were
only slightly smaller and didn't quite reach the waste. In the first
case some of the radioactive nuclides could become airborne, increasing
the Potential Hazard Index associated with the transuranics by several
orders of magnitude.

Based on the preceding considerations, 1t is possible to estimate
the probability of an impact for a specific waste repository. Assuming
that waste is buried at the depth of 300 m and is spread over an area
of 10 kmg, in a time period of 100,000 years (about four half-lives of
259

Pu), the probability of containment failure because of a meteoritic
impact would be about 10_7. It is interesting that the impact probability
of about 10—15/km2/year represents the order of magnitude of a risk beyond
human control (at least at the present time). Mankind seems to be little
concerned about the hazards of such unlikely, but potentially catastro-
phic, events. Actually, the consequences of the impact of a large mete-
orite could be so terrible as to make the exhumation of radiocactive waste
of' secondary concern. For example, an impact in a large urban area or

in the sea near a densely populated area could cause the loss of millions
of lives. For a fall in the sea it is believed that the main damage

would be caused by the resultant tsunami.

6.1.2 Volcanic Activity

 

The quantitative evaluation of the probability of occurrence of any
of the events still to be considered could be attempted only for specific
sites. An accurate knowledge of the regional geology would be an essen-
tial requisite. While, on the one hand, meteoritic impact can be con-
sidered a random process, volcanism, faulting, etc., are determined by
tectonic conditions. Hence, the following considerations will not result
in a numeric estimate of the risk of volcanism, but they may provide a
guide with respect to information that must be obtained if the risk has

to be minimized.
90

The geographical distribution of volcanoes that have been active
during historic times is very interesting. About 62% of all active vol-
canoes are located in the "circum-Pacific girdle of fire." Some 14% -
are in the Indonesian island arc. Only 24% are found in the rest of the
world; of these, 3% are on the islands of the central Pacific (Hawaii, .
Samoa, etc.), 1% on the islands of the Indian Ocean, and 13% in the At-
lantic Ocean (Azores, Cape Verde Islands, Canaries, Madeira, Iceland,
etc.). About 49 are located in the Mediterranean and northern Asia Minor.

Only the remaining 3% are located in mid-continental areas, and most of
them are associated with the African rift system.6'9

Geologic records indicate that several types of volcanic activity
have occurred in the past in mid-continental areas, although for some
types active examples are not known. Large volcanoes can be formed in
connection with a rift system. The African volcanoes mentioned above are
examples of this. Rift valleys are caused by large tensional forces, as
demonstrated by the normal faults and the grabens. Large tensional faults
have been responsible also for the genesis of the great lava plateaus of .
the world.6'lo The lava plateaus have been formed by the effusion of
lava from many fissures; very little explosive activity is associated t
with this type of volcanism. The lava is primary basalt (that is, not
differentiated), and this indicates that the source of magma is directly
associated with the mantle; therefore, the faults must cut the whole
Earth's crust. Examples of lava plateaus are the Columbia River Plateau
and the Snake River Plateau in the United States of America, the Deccan
Plateau in India, and the Parand Region in South America. Other vast
areas that have been covered by basalt are located in Ethiopia, Mongolia,
Siberia, Arabia, and Greenland.

Other types of continental volcanoes can exist in association with
mountain chains. Foreland volcanoes can be located hundreds of kilometers
away from the orogen; examples exist in France and in Germany. Ignimbrite
sheets, resulting from extremely explosive volcanic activity, are known
to be associated with ancient orogens in extensively peneplained continen-
tal regions.

Finally, we will mention briefly some very mysterious structures, .

of which the wells Creek Basin in Tennessee is one of the best-known
91

examples. The evidence for an explosive origin for these structures,
for which the term "cryptovolcanic" has been proposed, is rather strong.
However, no volcanic materials have been found associated with them.
Many geologists believe that the Wells Creek Basin and similar struc-
tures were formed by meteoritic impact. On the other hand, Bucher has
related several of them to structural axes and to other definitely

volcanic structures aligned along the axes.6'll’ 6.12

6.13

ation has been proposed by Goguel. '

A third explan-
If the hydraulic pressure of
water and other fluids contained in a permeable formation should locally
exceed the lithostatic pressure, the overlying strata would be lifted
into an arch. Upon fracturing of the strata and escape of the fluid,
the arch would then collapse, producing the chaotic structure observed.
Goguel's hypothesis is based on several reported observations of fluid
pressures vastly exceeding the hydrostatic pressure and even approaching
the total weight of the overburden.6'llL

From the point of view of volcanism, a high-level radiocactive waste
disposal site should be located in an area distant from the mobile belts

of the earth, tectonically stable, and without records of volcanic ac-

tivity in the last few million years.

6.2 Slow Geologic Processes

The slow geologic processes potentially capable of causing a release
of activity from a radioactive waste disposal formation are: (1) fault-
ing, (2) erosion, (3) leaching and transport by groundwater, and (U4)
plastic deformation of the disposal formation. The various processes
can be active contemporaneously and can be freely combined to give a
series of release mechanisms; for example, leaching and transport by
groundwater have to be preceded by some change in groundwater circula-
tion pattern since the absence of circulating groundwater is one of the
major requirements for a suitable disposal formation. The access of
groundwater to the waste could be a result of either faulting, erosion,
plastic deformation, or of a combination of two or more of these

processes.
92

6.2.1 Faulting
The probability of faulting can be minimized by locating the disposal

site in a tectonically stable area. However, the mechanical properties

of the disposal formation must provide additional safety features. Fault-
ing in hard rocks may result in a highly permeable fracture zone; there-
fore, hard rocks should not be considered acceptable for the ultimate
disposal of high-level waste. On the contrary, plastic rocks, such as
rock salt and unindurated shale, are able to flow and seal fractures if
under a sufficient geostatic load. Even in plastic rocks faulting might
have undesirable results if the offset of the two sides of the fault is
such as to destroy the integrity of an impermeable cover or to bring the
disposal zone into contact with an aquifer.

Movement along fault planes can occur in intermittent, occasionally
catastrophic slippages or in a more or less continuous creep. In the
great Alaska earthquake of 1899, an offset of almost 15 m was measured
on the main fault. ZFrom the point of view of waste containment, the me-
chanism of fault slippage is irrelevant; what is important is the possi-
ble rate of this movement averaged over a fairly long period of time. The
horizontal movement along the San Andreas Fault is estimated to be about
4 cm/year. No stable mid-continental area is likely to be subjected to
such high rate of movement.

Possible rates of vertical movement can theoretically be comparable
with the values for uplift and subsidence 1n the same areas as discussed
below. If the geologic materials deform as rigid blocks, the displace-
ment occurs mainly on fault planes, but in the case of relatively incom-
petent materials, uplift and subsidence could cause large-scale folding
and arching, but very little faulting might result. However, a rate of
vertical slippage of the order of a few millimeters a year seems quite
possible. It follows that the safety of disposal would be increased if
the disposal formation itself and the surrounding aquicludes were very

thick.

6.2.2 Erosion

In the previous chapter some values for rates of erosion covering a

rather wide range have been reported. With the average rate of erosion
il 4

95

in the United States (Table 5.2) of 6 cm/1000 years, 5 million years
would be required to remove an overburden of 300 m. We have seen also
that local rates of erosion can be many times higher than average values.
With a rate of erosion of 300 cm/1000 years, a 300-m overburden would

be removed in 100,000 years, or only four half-lives of 259Pu. While

500 cm/lOOO years is undoubtedly an exceptionally high rate of erosion,

it is still in the range of the locally possible values. In addition,

it is easy to postulate circumstances for which erosion could cause
radiocactivity to be released before the overburden is completely removed;
for example, in case of incision of an impermeable layer which, when
continuous, prevented circulating groundwater from reaching the depth of
disposal. Therefore, it is necessary to select a disposal site in an
area characterized by a low rate of erosion. In addition, all available
geologic information must indicate that no significant increase in the
rate of erosion is likely in the future. An increase in the rate of
erosion might be caused by climatic changes, such as variation of the
precipitation pattern or the advent of a glaciation, or by uplift of the
area. Increase of erosion caused by man through poor management of the
environment is not considered here, but may be of considerable importance.

At the present time, we are in no position to make accurate long-
term predictions about future climate; therefore, the most prudent action
is to select a disposal site in an area that has not been affected by
any of the Pleistocene glaciations. The implication is that what did
not happen in the past is not likely to happen in the future.

The possibility of predicting future vertical dislocations is some-
what better; indications might be obtained by present movements (if any),
by the regional pattern of gravity anomalies and by the thickness of the
crust. Much of the Earth's crust is in isostatic equilibrium. However,
many areas exist in which the crust is not in equilibrium. Among the
areas undergoing large-scale vertical movements, some tend to a restor-
ation of equilibrium, and, therefore, the driving forces are gravita-
tional. In many other cases the direction of movement is against isotatic
equilibrium; therefore, the driving forces are created by deep-seated
processes probably located at the boundary between crust and mantle.6'15

The nature of these processes i1s highly controversial, and the various
b

hypotheses are best considered only educated opinions. Among the hypo-
theses proposed are chemical reactions and differentiation, phase trans-
formations in the solid state, and rotating convection currents in the »
mantle. The picture is further complicated by the action of exogenous -
processes, continuously redistributing surface materials and, therefore, .
acting against isostatic equilibrium.

Table 6.1 shows possible types of vertical tectonic movements, ac-

15

cording to Gzovskii. In relation to waste disposal the important fact
is that data on present movements obtained with repeated high-precision
geodetic levelings, in addition to data furnished by geologic, geomorpho-
logic, and geophysic studies of the region, should enable one to make
predictions of future vertical displacement of the area.

The rate of vertical movement is quite variable with time; occasion-
ally, very high rates have been observed, mostly by means of frequent
geodetic levelings. It has been observed that there is a relation between
the maximum rate of movement and the length of time in which the movement
is averaged. In Fig. 6.1 is shown this relation as proposed by Gzovskii.
This figure shows that in 100,000 years the vertical displacement can be
LOO to 500 m in areas of high mobility and about 100 m in mid-continental '
areas. However, the data on uplift of previously glaciated areas show
that in particular circumstances Gzovskii's figures can be greatly ex-
ceeded. In the region of the Gulf of Bothnia, a good estimate for the
postglacial uplift is 600 m in about 15,000 years. With the curves of
Fig. 6.1, even if we consider Fenno-Scandia a highly mobile region, the
average rate of uplift in 15,000 years should not have exceeded 8 mm/year,
with a total uplift of 120 m. 1In the case of isostatic rebound of gla-
ciated areas, it must be considered that the melting of the ice caps has
been very rapid in a geological sense and, therefore, that the driving
force of the uplift has been established in a very short time. However,
it seems conservative to consider the curves of Fig. 6.1 as indicative
of likely rates of movement and not of maximum rates. It suggests that
uplift can, indeed, be fast enough to affect rates of erosion in a way
relevant to the waste-disposal problem. Therefore the disposal site
should be located in an area where the earth crust is in isostatic equi- .
librium and where no uplifting is occurring; subsidence on the other hand

might be a desirable feature.
Table 6.1. Possible Types of Deep-Seated Vertical Tectonic Movements

(From Gzovskii, 1963

)6-15

 

 

 

 

 

 

 

 

 

 

Sign of the
Types Direction IZ;Z:?E;C Cause Probability
Anomaly

Ia Directed against the uplift (+) + Mechanical displacements Undoubted
isostatic equilibrium on the top of the sub-

Ib (anti-isostatic) subsidence (-) - crustal layer

IIa In the direction meta- uplift (+) - Reaction to changes Probable
of 1sostatic equi- isostatic in thickness of the

ITb librium disturbed subsidence (-) + crust in its lower parts
by sub-crustal

II1a processes epi- uplift (+) - Reaction to anti- Possible
(endo-isostatic) isostatic isostatic displacements

ITTb subsidence (-) + of the crust

IVa In the direction of isostatic uplift (+) - Reaction to changes in Possible
equilibrium, disturbed by thickness of the crust

IVb exogene processes (exoisostatic) subsidence (-) + in its upper parts

 

 

 

 

 

 

S6
96

ORNL-DWG 70-6711

 

N31fi“-\\\\~ l
<>\\°\ HIGHLY MOB‘ILE REGIONS

100 —~o0 |

 

 

 

/: \I\

o

L

>

~ \
E 107! PLATFORM REGIONS ——
>

 

10~2 X

1073

 

 

 

 

 

 

 

 

 

109 10! 102 103 104  10° 108 10’
t, years

Fig. 6.1. Graph Showing the Dependence of the Average Velocity of
the Vertical Tectonic Movements (V) on the Duration of the Time Interval

of Averaging (t) (from Gzovskii, 19656'15)-
97

The risk of excessive erosion would be greatly reduced if the reposi-
tory were located in an area of low elevation and low relief, with the
disposal formation possibly below sea level. Even in this case, erosion
would be theoretically possible in a few instances, mainly in case of new
episodes of glaciation that might combine the high-scouring power of gla-
ciers with the eustatic lowering of sea level or in case of uplift of the
area.

It is clear, however, that in case of total failure of the geologic
forecast and very high erosion rates, the time required for the removal
of the overburden would be so long that 259Pu would be the only radionu-

clide to be brought to the surface in significant amounts.

€.2.3 Leaching and Transport by Groundwater

 

All high-level waste-disposal schemes have in common the selection
of a disposal environment without circulating groundwater. Many geologic
materials can be considered essentially impermeable if no fractures are
present. Laboratory samples of massive limestone or basalt show extremely
low permeability, but these formations are often among the best aquifers,
because water movement occurs through joints and fractures. All rigid
rocks can become very permeable when fractured. Rock salt and plastic
shale flow easily under relatively moderate pressure and would seal open-
ings and fractures.

At the present time, disposal in natural salt formations is the most
practical and favored solution to the problem of radioactive wastes. Be-
sides the ease of deformation, salt has additional advantages such as high
thermal conductivity and the ease with which it can be mined. However,
when rock salt comes into contact with groundwater, dissolution occurs.
The rate of dissolution varies with the volume of water coming into con-
tact with the salt per unit time, but given a long enough time of leach-
ing with unsaturated water, all of the salt would eventually be removed.
Therefore, in all cases in which salt beds have been preserved for geo-
logic times in their original stratigraphic position, one can conclude
that the salt has not been exposed to leaching by groundwater. Since the
evaporitic sedimentary cycle begins and ends with phases of argillaceous

sedimentation, salt is normally protected from dissolution. Tectonic
98

movements or erosion may cause failure of the sealing and leaching of the
salt. 1In fact many examples of leaching of salt are known. At times the
tectonic movements are extreme, as in the case of diapirism, but in other -
cases leaching resulted from moderate folding and faulting. In most of
the known cases, evaporites were leached from above, but in a few cases .
salt has been leached from ‘below.6'l6 Borchert and Muir report the in-
teresting case of the Middle Muschelkalk evaporites of southern Germany,
which were often leached from the basal limestone upwards, and in places
almost completely removed.

For a waste repository located in a salt formation, the probability
of leaching must be negligible. This can be assured if the following
conditions are observed at the site.

1. The shale beds, both below and above the salt, are thick and
continuous over a large area.

2. The salt formation is thick, and the waste is located far from
the salt boundary.

3, The shale bed above the salt is so deep below the surface that
no erosion process can reasonably affect its integrity in a time span of
several hundred thousand years. i

4. The region is tectonically stable.

These problems have been faced in considering bedded rock salt as a
disposal medium, and it has been concluded that these conditions can be
met.

Some shale formations with suitable physical properties might offer
an alternative to salt as disposal medium. The plasticity of shales is
a function of several factors: (1) the mineralogical composition of the
sediment, (2) the size distribution and shapes of the particles, (3) the
amount of connate fluids, and (L) the electrolytes present in solution.
The amount of water is the most important factor and depends on the com-
paction the shales have undergone. Compaction depends on the pressure
and the length of time that have been available for the elimination of
connate water.6'l7’ 6.18 "

Well-compacted shales are quite competent and deform by fracturing.
Shales that are not compacted beyond a certain limit, either because they

have never been subjected to the necessary pressure or because they did
99

not lose the connate fluids, deform by flowing. Many examples are known
of the plastic behavior of these materials, such as diapiric structures
with a shale core, mud lumps, mud volcanoces, and clay glaciers. Finally,
countless more examples are furnished by the oil industry, which had to
develop special techniques for drilling through unstable shale formations.
While the feasibility of disposal of high-level solidified wastes in
19

salt formations has been demonstrated,é' very little work has been done
on other geologic materials. Therefore this discussion is highly specu-
lative. It seems, however, that, in comparison with salt, shales might
present some advantages as well as disadvantages. The advantages are the
much longer expected life of the waste containers, the insolubility of
the shales, and their high ion exchange capacity. The disadvantages of
shales are their low thermal conductivity, the relatively large amount

of water contained in the pores, and the difficulty of mining. While the
poor removal of decay heat and the presence of pore fluids are not be-
lieved to cause insoluble difficulties, the problem of mining and oper-
ating a disposal facility in a plastic shale formation might well be
critical.

From the point of view of the risk of leaching of the waste, disposal
in shale would be quite different from disposal in salt. With the excep-
tion of small quantities of brine trapped in minute noncommunicating cavi-
ties, salt is completely free from water. Since it is very soluble, it
has been preserved only where shale beds have protected it from leaching.
On the other hand, plastic shales must be very porous and contain large
volumes of water, since the plasticity is caused by the pore water. But
the permeability of plastic shales is so low that any appreciable move-
ment of water through them would require long times. The rate of movement
of cations or particles contained in the water would be orders of magni-
tude lower than the velocity of the water itself. The migration of ions
through the shales in the absence of water movement would be controlled
by the mechanism of molecular diffusion.

The following examples are an indication of typical rates of movement
by molecular diffusion through an average plastic shale. (See also Ap-

90

or the average movement would be a few meters in 1000

137

pendix A.) For

years; in the same time Cs would have moved only a few centimeters.
100

For americium and plutonium the time necessary to move a few meters away

5

would be respectively 107 and 106 years. More elaborate calculation
would be necessary if the initial solid State of the waste and the effect -
of decay heat on the shale were to be considered. -
In the case of disposal in salt, there would be no leaching of the -
waste by water. If dissolution of the salt were to occur, leaching of
radionuclides would follow; this would require a large flow of groundwater.
The only correct approach to the selection of the disposal formation
1s to check the proposed geologic environments against the very stringent
safety standards required by the magnitude of the potential hazard. Only
after an alternative type of formation has been found acceptable from
the point of view of safety should elements such as convenience of oper-
ation and cost play their part in the selection. Salt formations appear
to meet the safety requirements, and at this moment they represent the
most practical solution. However, many areas of the world exist without
sultable salt formations. In this case, shale formations might well pro-
vide an acceptable alternative, but considerable efforts would need to be

expended to assure that safety requirements were not being compromised.

e

6.3 Plastic™ Deformation of the Disposal Formation

It has been stated that a suitable disposal formation must be char-
acterized by the absence of circulating groundwater and by plasticity.
Since some plastic deformation occurs in practically all rocks, it is
clearly the rate of deformation required in a disposal formation that
must be defined. For example, the creep of limestone has been extensively
studied, and many laboratory experiments have defined the deformation
curves for this rock material. However, field observations in a large
depth range prove that the creep rates are not sufficient to close frac-
tures formed in this rock. Instead, once water circulation is estab-

lished through a fracture, the dissolution of calcium carbonate will

 

aThe term plastic is applied to the continuous deformation of com-
plex solid bodies, such as rocks, in contrast to the viscous flow of
fluids. It is used without any implication about the mechanisms respor-
sible for the deformation.

ew
te

101

progressively enlarge the opening. In this case, the rate of closure of
the openings because of the creep of the rock is certainly less than the
rate of dissolution.

Therefore, it is evident that creep rates in the disposal formation
must be higher than the creep rates of limestone. It is not true, how-
ever, that the higher the plasticity the better. Beyond a certain limit
of deformation rate, the problem of operating the facility would become
insclvable. Since salt has fairly consistent physical properties, it can
be stated that, in this material, troublesome rates of deformation would
be met at depths exceeding 800 to 1000 m. Argillaceous sediments, on the
other hand, present a tremendous variability in physical properties. 1In
a general way, plasticity decreases with increasing compaction and there-
fore with depth of burial; however, the relation is far from straightfor-
ward. In fact, many factors contribute to determine the physical
properties of argillaceous sediments, especially the mineralogical
composition, the stratigraphic relationships, and the geologic history.
As a consequence, no generalization is possible about the depth to which
shales of éppropriate plasticity could be found. The only way to learn
about the physical properties of a shale formation is through actual
field measurement and observation of tectonic deformations, if any.

The capability of plastic deformation of the disposal formation
represents the main safeguard against a sudden loss of containment and
release of radioactive nuclides to groundwater. However, this feature
might have negative consequences 1f the disposal formation were to be
subjected to excessive deformation. Therefore the possibility of the
disposal formation being affected by diapiric processes must be investi-
gated and the possible extent of deformation throughout a time period
of several hundreds of thousands of years must be evaluated.

Diapirism is a process by which earth materials from deeper levels
have deformed and pierced the overlying strata. For diapirism to occur,
the necessary conditions are: the existence of a plastic formation and
its exposure to a pressure difference sufficient to cause flowage. If
the flowage must continue for a long time in order to result in the in-
trusion through the overburden of large volumes of diapiric material,

other conditions must be realized; either the diapiric material must have
102

a lower specific gravity than the overburden or tectonic processes must
actively squeeze the plastic materials through the overburden. Diapiric -
processes of evaporites and argillaceous sediments are not necessarily »

identical and they will be reviewed separately. .

6.3.1 Salt Diapirism

The process of salt diapirism progresses from the undisturbed hori-
zontal bed through many intermediate stages of deformation before reaching
the state of a well-developed diapir. Linear salt structures result from
the flowage and accumulation of salt in elongated zones of reduced pres-

"non

sure. Examples of linear structures are "salt anticlines, salt pillows,"

"salt ridges," and "salt walls." Unless salt intrusion occurs along a

fault plane, the linear structures arch the overlying strata but do not

pierce them. Along the linear structures there are sites of minimum pres-

sure where the accumulation of salt is concentrated. On the sites of

maximum salt accumulation subcircular structures start to develop. Before

piercing of the overburden, the localized accumulations are called "salt -

uplifts"; after piercing they are called "salt diapirs," "salt domes,"
S ) 2

" n mon !

"salt chimneys," "salt plugs," "salt stocks,” and "salt eczemes." Where

5o

more dlapirs merge at depth into a salt ridge, the whole complex is called
"salt massif." It is also possible for the salt accumulation to begin
directly in a subcircular area without a linear stage.

There are linear structures that have given origin to multiple di-
apirs; in these cases an alignment is usually evident. The Five Tslands
group and the Bay Marchand-Timbalier Bay-Caillou Island group, both in
Louisiana, are examples of diapir alignment because of common roots in a
deep linear structure.6'20’ 6.21

Day Dome, Texas, 1s an example of a salt anticline that has resulted
in a single diapir.é'22 In the upper portions diapirs are typically cir-
cular or oval in horizontal section, with a diameter usually between 2
and 8 km. In depth, the shape is grossly cylindrical, with occasional
overhangs, or conical. >

The depth of the mother bed controls the maximum height that salt
diapirs can achieve. In the diapiric province of the Gulf Coast of the .

United States, no well has ever reached the mother bed, which is believed
103

to be at least 8000 to 9000 m deep. In the east Texas and north Louisi-
ana synclines, the Louann salt lies at depth ranging between 3000 and more
than 4500 m.6'25 In the German salt basin the mother bed depth ranges
between 3000 and 5000 m.6'2u In northeastern Algeria the total depth to
the diapiric Tfiassic complex is of the order of 3500 to 5000 m.6'25 In
south Iran the depth to the mother bed is 6000 to 8000 m.6'26’ 6.27

It is, therefore, clear that salt diapirs are usually large struc-
tures requiring many cubic kilometers of salt. An example of an excep-
tionally large structure is the Lake Washington dome, Louisiana, which,
according to the estimate of Atwater and Forman, contains more than 1000
km5 of salt.6'21 The same authors have calculated that the salt massif
formed by the merging at depth of the Bay Marchand-Timbalier Bay and
Caillou Island diapirs, Louisiana, contains in excess of 5500 km5 of
salt. To supply the volume of salt present in this last structure, the
necessary thickness of salt in the source érea has been estimated to be
of the order of 4 to 5 km. Undoubtedly, this is an extreme value, but
the existence of a thick salt series is one of the necessary conditions
of salt diapirism. The critical thickness below which salt diapirism
does not occur is unknown, but it is probably true that in the instances
when diapirs developed the mother bed must have been at least 300 to 40O
m thick.

The existence of a thick layer of salt, although necessary, is not
a sufficient condition for the formation of salt diapirs. Sannemann6'28
refers to the region northwest of the salt-stock family north of Hamburg,
where, in a large area, Zechstein salt, about 1000 m thick, covered by
3000 to L4000 m of sedimentary overburden, lies on a basement rising north-
ward with a slope of 1 to 2°, Apparently, no salt deformation, even to
the initial stage of formation of salt pillows, has occurred; instead,
the salt has maintained its original uniform thickness. It is also evi-
dent that burial under a sedimentary cover, 3000 to LOOO m thick, is not
in itself a sufficient condition to initiate the flowage of salt. In
other areas of Germany there is good geologic evidence that salt deforma-
tion started when salt was only 2000 m deep.

One can conclude that the plastic deformation of salt begins where

and when the salt is exposed to a sufficient pressure difference. The
104

stresses acting on the salt bed and responsible for its flow are caused

mainly by differential loading. Tectonic forces can also be important

in increasing the possibility of differential loading or in actually .
squeezing the salt along fault planes. An example of the first case -
would be a sedimentary basin, with a thick salt series at the depth of .

1000 m, which is subjected to folding. The differential accumulation
between synclines and anticlines would then result in differential load-
ing of the salt. Once the critical pressure difference has been reached,
salt begins to flow from high-pressure to low-pressure zones. The over-
burden would tend to follow the deformation of the salt bed, sinking in
the space vacated by the salt and being uplifted over the area of salt
accumulation. Reduced accumulation or even erosion on the area of uplift
and increased accumulation on the sinking area would maintain or even in-
crease the pressure difference responsible for the flowage of salt. Even-
tually the shear strength of the overburden over the zone of uplift would
be exceeded, and fracturing of the cover and salt intrusion would occur.
After piercement of the overburden, the vertical movement of the salt
would be concentrated at the site of piercement, and the rest‘of the salt
uplift or salt anticline would collapse. At the surface, a syncline ’
would form on the site of the previous salt uplift. Salt intrusion could
be arrested either because the pressure difference is no longer sufficient
to cause flowage or because no more salt is available in the source area.
The second possibility could be caused either by depletion of salt in the
source area or because the salt supply is cut off by the peripheral sink.
If no more salt is available to flow into the salt structure, the upward
movement of salt would terminate. If, instead, the salt intrfision were
arrested because the resultant of forces were not sufficient to overcome
the resistence to salt movement, a future reactivation of salt intrusion
would be possible.

The forces acting on the salt and responsible for its deformation
change with time as a function of several factors. 1In addition, the
physical properties of salt change as a function of temperature, confin-
ing pressure, crystal size, impurities content, and strain hardening.

In the stage of salt deformation before the piercement of the over- .

burden, the horizontal component of salt movement prevails,\and the force
105

causing the movement is essentially due to differences in weight on the
salt bed. After piercement, part of the salt mass moves upward. With
the growth of the diapir, the difference in density between salt and
sedimentary rocks gains importance in determining the forces acting on
the salt body. The specific gravity of salt is about 2.2; on the other
hand, terrigenous sediments are very porous at the time of deposition
and undergo compaction depending on the pressure to which they are ex-
posed. Figure 6.2 shows the relationships between the density of clayey
sediments and the depth of burial observed in different geologic areas.
Dickinson's curve is the one best approaching the case of geologically
recent shales.6'29

If the salt is intruded through sediments with density higher than
2.2 g/cmB, the load on the mother bed below the growing salt structure
varies inversely with the height of overlying salt. Therefore the pres-
sure difference driving the salt flowage into the diapir is directly |
proportional to the height of the diapir itself. This is only true as
far as the intrusive salt replaces the heavier sediments of the over-
burden; if the growing salt structure compacts or uplifts the overlying
sediments, the load below the growing diapir increases with the height
of salt, and the pressure difference driving salt in the diapir decreases.
When the overburden is uplifted above the growing diapir, intrusion can
continue only as long as the necessary pressure difference is maintained
by differential accumulation between uplift and surrounding area and/or
erosional unloading of the uplift.

Once the top of the growing diapir reaches circulating groundwater,
salt dissolution begins. The insoluble materials contained in the salt
are left behind and accumulated. In the Gulf Coast area salt 1s usually
very pure; total insolubles are a few percent of the total mass; anhy-
drite constitutes about 99% of all insolubles.6'50

The leaching of the salt and the accumulation of insolubles result
in the production of the cap—rock formation present on many diapirs.
Occasionally, the volume of cap rock is very large, indicating that dis-
solution of salt has progressed for a very long time and that a very
large volume of salt has been removed. For example, Bornhauser calcu-~

lates that the accumulation of the cap rock present on top of Day Dome,
106

ORNL-DWG 70-2344

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

28 T T T [ L T
APPROXIMATE SHALE — MINERAL DENSITY 2.65
{ 3
g —
. 2.4 [~ ATHY DICKINSON
=
2 2
Ll
a 2.0 | HEDBERG
w
—’ -
<
I :
w
1.6
1
1.2
0 1 2 3 4 5 6 7 (x103)

DEPTH (meters)

Fig. 6.2. Average Relationships Between Shale Density and Depth.
Curve l--determined by Athy for Paleozoic shales in Oklahoma. Curve 2--
determined by Hedberg for Paleozoic shales in Kansas. Curve 3--deter-
mined by Dickinson for Cenozoic shales in the Gulf Coast Area.
107

5 of salt.6'22 Such

Texas, has required the dissolution of about 45 km
volume of salt would make up a layer of salt about 6000 m deep. Since
the top of Day Dome could never have been 6000 m higher than the present
level, the dissolution of salt must have progressed contemporaneously
with the rise of salt in the diapir. It follows also that the rates of
the two processes must have been of the same order of magnitude.

If the rate of growth of the diapir exceeds both the rate of salt
dissolution and the rate of sediment accumulation, salt can reach the
surface. Once the diapir has reached the surface, the rise of salt can
be terminated only by the depletion of salt in the source area or by the
formation of a salt mountain high enough to compensate by its weight the
pressure difference driving salt from the source area into the diapir.
Salt diapirs reaching the surface are known only in areas characterized
by a very arid climate, such as northern Algeria and south Iran. In
south Iran the salt diapirs reaching the surface are numerous, and oc-
casionally salt forms true mountains as high as 1200 m above the level
of the surrounding plain. With the assumption that the 1200-m-high salt
mountains are in isostatic equilibrium, the mother bed should be at a
depth of 7000 to 8000 m. Probably the mother bed is even deeper, because
surface processes, such as erosion and lateral spreading of salt under
its own weight, should prevent attainment of isostatic equilibrium. It
seems, therefore, that the final termination of diapir growth would have
to be caused by the eventual depletion of salt in the source area. In
some cases the growth of salt diapirs could be arrested by the accumula-
tion of a great thickness of sediment above the rising structure. In
this case, it is necessary that the rate of sedimentation exceeds the
growth rate of the diapir.

One aspect of salt diapirism that is very important in relation to
the safety of waste disposal is the rate of the précess in its various
stages. If the time‘necessary for an unacceptable deformation of the
salt bed should largely exceed the time required for decay of 259Pu to
innocuous levels of activity, the whole problem of the plastic deforma-
tion of salt would have little relevance to the disposal of radioactive

waste.
108

In the abundant literature on salt diapirism, several estimates of
the rate of diapirs' growth can be found. Most geologists believe that
salt deformation is a slow process and that the actual rate of growth of
salt diapirs is of the order of a few millimeters per year. The rate
of salt movement is not the same in all phases of salt deformation; it
is probably at a maximum in the later stage when diapirs are approaching
or reaching the surface. 1In fact, in this phase the pressure difference
due to the salt-sediment density contrast is close to its maximum and
the resistance offered by the overburden to the rising salt is very re-
duced or even nil when salt is exposed to the surface. In the prepierce-
ment stages of salt deformation, the pressure differences are much less
and the resistance of the overburden is higher; therefore, even consider-
ing the higher temperature of the salt, because of the greater depth, the
rates of movement should be markedly less than the rates of growth of a
well-developed diapir approaching the surface. Of a quite different
opinion is Tursheim, who reports Sannemann's conclusion that in Germany
the average rate of salt movement on the geologic time scale is 0.3

6.24

mm/year. Surprisingly, Sannemann found that the flow rate of 0.3
mm/year was roughly constant, both in the prediapiric stage of salt pil-
low and salt anticline formation and in the mostly vertical flow of the
diapiric stage. It might be possible to reconcile these two opposing
points of view, considering that the 0.3 mm/year is a flow rate averaged
over geologic time periods. In the stage of salt pillow formation, the
physical conditions of the salt bed and the relations between salt and
overburden are essentially uniform; therefore, a continuous, uniform
flow of salt is probable. In the diapiric stage the situation 1s quite
different: salt rises through progressively colder sediments that must
be forcibly broken and pushed apart. The resistance offered by the over-
burden to the rising plug changes markedly as a function of the faulting.
Therefore, an irregular, discontinuous movement seems the most logical
mode of diapir growth.

Borchert and Muir conclude their review of the problem stating that
the usual rate of diapir growth is probably less than 2 mm/year.6'16 At

times the relationships between salt and overlying sediments permit the

reconstruction of a long and complex history of salt emplacément. Atwater
109

and Forman describe several diapirs for which a history of salt emplace-
ment extending during many millions of years can be followed.6'21 An ex-
ample is furnished by the Iowa salt diapir in Louisiana, depicted in

Fig. 6.3, for which several phases of uplift are known. It is interest-
ing to note that the accumulation of oil is related to a fossil "high"
caused by the Oligocene-Miocene uplift and not to the axis of the more
recent uplift located about 1500 m south. The displacement along the
major fault is clearly caused by the youngest phase of uplift. This
fault can be traced to within 450 m of the surface.

Borchert and Muir6'16 report Lotze's observation that, in Spain,
rising diapirs of Keuper salt influenced the thickness of sediments ac-
cumulated throughout the upper Cretaceous. A very limited thinning can
be detected in the Cenomanian sediments, but it becomes quite apparent
in the Turonian and very marked in the Senonian. Above the diapirs, the
whole upper Cretaceous succession is often less than a tenth as thick as
in the surrounding area. The only logical explanation is continuous
growth during all this time period. A similar situation is probably oc-
curring in several present basins as will be discussed below.

Considering the complexity of salt deformation and the many parame-
ters that can actively modify the forces acting on the salt and the physi-
cal properties of the salt itself, it is no surprise that diapir growth

6.13, 6.32 and Muehlberger6'55

is not a regular, uniform process. Balk
have studied the internal structures of several salt domes, in which
mining operations have been conducted, and concluded that salt advances
in spines and lobes separated by shearing planes. The salt movement is
probably jerky and irregular; possibly phases of diapir growth are sep-
arated by periods of stasis.

As already mentioned above, the relationship between cap rock,
underlying salt, and surrounding sediment, illustrated by many diapirs,
is strong evidence that the rise and the dissolution of salt have pro-
gressed at comparable rates. Additional evidence about the rate of salt
deformation can be obtalned with the following‘considerations.

1. Anomalously high temperatures have been observed in several salt

structures. These temperatures seem to be adequately explained by the

high thermal conductivity of salt and by the heat generated by internal
110

ORNL-DWG 70-6726

 

 

 

 

 

 

 

 

 

 

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T e oo e s ek s e = - Top =
Aoz d===1- —AS - = " = OF i -
de oo =8 SALT -
3000 —1— — et 5 5 =
?Re ‘Qfi!flflbfik" ] =
,_.4—-—{// '. LOCUS OF ‘\
7 //0‘0’0‘0’0‘0’0’0’0’0‘ 4 POST MIOCENE”™D ”
00 LATE OLIGOCENE 00‘ UPUFT
4000 AKX SALT CORE 20XXXR

 

 

x9§§§§Q§§QQQQQQQQ§§§§§Q%&/XZS/\/\/\/& =

 

O 1 2
1

KILOMETERS

—

 

 

 

 

Fig. 6.3. North-South Structural Cross Sect%on Iowa Salt Dome;
No Vertical Exaggeration (from Atwater and Forman )
111

friction during salt deformation. The uniformly high temperatures with
maximum values at the center line of the diapir which would be expected
in young salt structures which have intruded very rapidly have never
been observed.6'ELL
2. Seismic profiles through the bottom sediments of the Gulf of
Mexico and other sea basins show many structures that strongly suggest
growing diapirs. The drilling of one of the Sigsbee Knolls located in
the very flat Sigsbee Abyssal Plain, in the deepest part of the Gulf of
Mexico, under about 3600 m of water, has proved that these small hills

6.35

are the sea bottom expression of salt diapirs. While a large frac-
tion of the abyssal plain sediments is constituted by turbidites, all
sediments cored on the Challenger Knoll down to the cap rock are pelagic.
Since the cap rock is overlain by sediments of upper Miocene age, it is
demonstrated that this salt diapir has caused a topographic relief suf-
ficient to prevent accumulation of turbidites for several million years.
The thinning of sediments on the flanks of the Knoll, as revealed by the
seismic reflection profiles, strongly suggests growth during sedimenta-
tion. ©Some of the thinning is caused by differential compaction between
the thick turbidites and their pelagic equivalent on the Knoll. However,
downbuilding cannot be the main process at work, or the Knolls would be
rapidly buried under the accumulating sediments. Hence a rate of diapir
growth of the same order of magnitude as the rate of sedimentation seems
the most logical explanation of the existing relationships.

5. The study of rim synclines furnishes additional evidence about
the evolution of salt structures. The downwarping of the sedimentary |
strata into the space vacated by the flowing salt is necessarily con-
temporaneous with the accumulation of salt in the area of uplift. Figure
6.4 shows the diagrammatic cross section of a salt diapir and associated
rim syncline, based on observations of German salt structures. Clearly
the development of the rim syncline has been a very long process. Ac-
cording to Sannemann's diagrammatic reconstruction, no salt deformation
occurred until Keuper time (upper Triassic). No piercement occurred
until middle Jurassic time, thus allowing about 30 million years for the
accumulation of salt in the salt pillow. The intrusion of salt was ter-

minated in upper Cretaceous time because of the depletion of salt in the
112

ORNL-DWG 70-6729
MIDDLE JURASSIC
UPPER JURASSIC
LOWER CRETACEQUS

 
 
  
   
 

LOWER JURASSIC

 

 

 
  

 

  

 

 

 

 

 

 

 

 

 

 

 

80
TERTIARY __ _UPPER CRETACEQUS 41400 o
/ UPPER CRETACEOUS LOWER CRETACEOUS ~ | | ' &
ST/ T T TRESALT PLUG UPPER JURASSIC 5
— “/QH ; ~ MIDDLE JURASSIC™ ~ ] 140
== UPPER TRIASSIC e ‘T VOWER JURASSIC g
= S — -~ —UPPER TRIASSIC —— 1160 1
MIDDLE TRIASSIC MIDDLE TRIASSIC 180 §
LOWER TRIASSIC
| ! 200
|

- SALT MIGRATION ——-————-—-5

E==] PRIMARY PERIPHERAL SINK
™™ SECONDARY PERIPHERAL SINK

Fig. 6.4. Diagrammatic Cross Section of a German Salt Diapir and
Associated Rim Synsline. Notice migration of the axis of the rim syn-
cline through geologic time and resulting pseudo-anticline with axis

located on the site of the primary sink. Designed by Sanneman. (From
Trusheim,6.24.)
113

source area. Therefore, the stage of active diapirism must have lasted
for a time period of the order of 30 to 40 million years. The resulting
average rate of movement of the ascending salt is exceedingly slow. If
the evolution of the rim syncline can be reconstructed and if the struc-
tural relationships between the salt and surrounding sediments are known,
the geologic history of the salt structure can be deduced. Unfortunately,
the data necessary for an accurate geologic reconstruction for most salt
structures are not available. For example, in the Gulf Coast area rim
synclines of Cenozoic age are fairly well known, but the older synclines
are too deep to be reached by even the deepest wells.

4. Evidence of the rate of salt movement is offered by several ob-
servations of present movements. The reported movements have been observed
either in mines located in salt diapirs or at the surface on top of shal-
low salt diapirs. Caution 1is necessary in the interpretation of deforma-
tion data obtained in salt mines, because closure of mined cavities always
occurs, occasionally very rapidly.6'2LL In the instances of observed up-
1lift, the possibility of subsidence of the surrounding area because of
compaction of the sediments should be analyzed. However, a few cases of
salt movement seem certain, and it is likely that many more instances
could be revealed if the appropriate measurements were conducted. For
deep diapirs the observation of movements would be expected to be more
difficult, both because of the likely slower rate of salt uplift and
because part of the movement would be absorbed by the compaction of the
overlying sediments. It seems likely that micro-seismic data would furnish
a valuable tool to investigate the growth of salt'diapirs, especially in
depth, but no observation of this nature is known to the authors.

Lotze is quoted by mentioning that a relative uplift of 1 to 2 mm/year
has been measured on salt stocks of the Casplan depression. - 2k Trusheim
reports Teichmuller's conclusion that the rise of the salt stock of
Segeberg, in Holstein, northern Germany, has been about 2 mm/year in the
last 20,000 years.6'2LL From observations by Lees and Falcon, Trusheim
has calculated a rate of salt movement of 2.4 mm/year in salt structures

6.2k

located in Iragq.
11k

Sheets reports that active movement has been measured at Hoskins

6.36

Mound, Brazoria County, Texas. An area of 100 acres located in the
central part of the diapir has risen a maximum of 18 cm in a 23-year
period (1922-1945). The resulting rate of uplift at the surface is about
8 mm/year. Due to the known subsidence of the surrounding area, this rate
of uplift could be an overestimate. Still it could be the beginning of
a salt spine, such as those present at Anse La Butte (St. Martin Parish),
Jefferson Island, and Belle Isle in Louisiana.

Muehlberger and Clabaugh report that in 1937 part of the mine located
in Winnfield Salt Dome, northwestern Louisiana, was accidentally flooded

6.37

causing a water-etch line. After 27 years the etch line was no longer
horizontal, but showed a deformation amounting to several centimeters.

In a railroad cut on the north slope of Jefferson Island, brackish
water fossils were found in loose sand, 6 to 9 m above sea level.6'31’ 6.8
The fossils were identified and found to be probably of lafie Pleistocene
or early Holocene age. If more accurate dating should confirm the age of
these fossils, the logical explanation would be that at the beginning of
the Holocene, 11,000 years B.P., the sand was accumulated in a brackish
water marsh located at sea level; from this it would follow that the de-
posit has been uplifted to the present level during this span of time.
Considering that 11,000 years ago sea level was about 30 m below the

6.39 the uplift could have been 30 to 4O m in a time span

present level,
of 10,000 to 15,000 years, which gives a rate of growth of 2 to 4 mm/year.
It is worth noting that also at Jefferson Island only part of the salt
core is actively rising. The major part of the diapir terminates in a
flat surface at the depth of about 250 m. On the southeastern edge of the
diapir a spine rises to the average elevation of the surface in the area.
However, no salt is exposed at the surface, as about 20 m of sediments,
overlying the salt spine, were arched to form the hill called Jefferson
Island.6'ho

Vaughan reports also that near Shaft Hill on top of the Belle Isle
diapir, one of Louisiana's five islands, a conglomerate bed with strike
N. 750 E. and dip 250 NW is exposed.6'58 The fossils in the conglomerate
are all species represented on the Gulf Coast today. It is clear that,

since accumulation, this conglomerate has been tilted to an angle of 230.
115

In this case the data are insufficient to calculate the rate of uplift,
but the evidence of recent movement is inescapable.

Finally, there is the observation that of the thousands of salt
structures known throughout the world, none has ever been observed to
undergo rapid growth. Since all stages of development of salt struc-
tures can be observed, it seems that only two conclusions are possible.
The first is that the geologic process of salt diapirism either has been
eliminated or only occurs when nobody is looking. The second possibility
is that salt diapirism is regularly occurring, whenever conditions are
appropriate, but only accurate measurements or geologic observations can
provide evidence of the slow rate of movement. |

In conclusion, it seems fairly well proven that the risk of contain-
ment failure because of diapir formation is negligible if the waste re-
pository is located in a salt formation that meets the following
conditions:

1. It should be a bedded salt formation showing no evidence of
plastic deformation in the recent geologic past and located in a tec-
tonically stable area.

2. The salt bed should be close to horizontal, and the surface
relief should be minimal to insure a very limited differential loading.

3, The thickness of the salt bed should be adequate to furnish
safe containment but less than the 300 to 40O m necessary to produce
sizable salt structures.

. The salt bed should not be located at great depth where the
plasticity of salt is increased by the high ambient temperature. However,
this is only a theoretical problem, because the maximum depth is limited
much more drastically by the required stability of mined cavities than
by the need to prevent excessive plastic deformation of the salt forma-
tion. On the other hand, a depth of at least 300 to 40O m seems desir-
able to remove the waste from geologic processes active at or near the
surface.

While salt diapirs certainly exist for which no future salt uplift
igs possible because of depletion of salt in the source area, the demon-
stration of the safety of disposal in a salt diapir would require very

extensive geologic investigations. In addition to the structural
116

problems, diapirs would present much more serious hydrologic problems,
because of the complexity of groundwater circulation in the adjacent
fracture zone and because of the possibility of temporary permeability

of the salt mass in correspondence with shearing zones.

6.3.2 Shale Diapirism

 

The plastic deformation of argillaceous sediments has many aspects
similar to the deformation of salt, but in many ways it can be quite dif-
ferent. The basic mechanism is always the flow of a plastic medium when
exposed to the appropriate pressure difference. The differences in be-
havior between salt and shale are due to the extreme variability of the
physical properties of clayey sediments. Shales with "equivalent vis-
cosity" and density similar to those of salt would be expected to undergo
deformation processes of diapiric nature. As a matter of fact, in the Gulf
Coast area many masses of diapiric shales have been identified.6'ul’ 6.h2
The interest in these structures is due largely to the hydrocarbons that
may be trapped on the flanks of the shale masses or accumulated in the
structural highs overlying the diapiric bodies. In many instances shale
masses are intruded along with salt to form a single diapiric core. 1In
other cases there is only one intrusive material.

Diapiric shale is characterized by a high pore fluid pressure in
addition to low resistivity, density, and sound transmission velocity.
These physical properties allow the outlining of shale masses by geophysi-
cal methods. The low velocity of sound transmission within the shale mass
permits differentiation from a salt mass that would be undistinguishable
on the basis of gravimetric and seismic-reflection data only.

The abnormally high fluid pressures in diapiric shales are due to
the relatively high rate of sedimentation and to the very low permeability
of the sedimentary complex, especially across the bedding.é'MB’ 6.1l
Under these conditions, the rate of escape of connate fluids from compact-
ing sediments is less than the rate of sediments accumulation; therefore,
the trapped fluids prevent compaction and support part of the welight of
the overburden. As a limit, if no fluids could escape, essentially no

compaction would occur and A, ratio between fluid pressure and overburden

pressure, would be equal to 1. TFigure 6.5 shows the relatiohships between
117

ORNL-DWG 70-6712
‘[ T

FLUID PRESSURE

 

_—

 

 

 

 

 

 

 

 

 
     

 

 

 

0.35 | - ]
\\\\\ \\;\\ OVERBURDEN PRESSURE
\ 0.96
0.30 9. %€
\ \
: 0.94 \
0.25 —
n ~ \
8 0.20 \ -
o
a
“ 045 N\\\> \\\\\g
0.10

 

 

 

 

0.05 —— NORMAL
HYDROSTATIC

CONDITIONS A=0.465 (ATHY)
0 1 j \*"
0 1000 2000 3000 4000 5000 6000

 

 

 

 

- ,DEPTH (meters)

Fig. 6.5. Mutual Relationships of Depth, Porosity, and Fluid
Pressure-Overburden Ratio in an Average Shale or Mudstone. Athy's
Curve Assumed to Represent Condition of "Compaction Equilibrium."
(From Rubey and Hubbert.0.4h)
118

depth and porosity for various values of A in an average shale. Athy's

curve (see also Fig. 6.2) represents a pore pressure equal to the normal
hydrostatic value. Cases of A as high as 0.9 have been reported by sev-
eral authors. Thomeer and Bottema report examples for which fluid pres-

L5

sures are even higher than 0.9 times petrostatic pressures. According
to these authors the petrostatic pressure is an upper 1limit that fluid
pressure can never exceed. While this is undoubtedly true for most cases,
it is theoretically possible for the fluid pressure to exceed the petro-
static level in at least two cases: (1) If erosion, either subaerial or
submarine, or slumping removes part of the overburden, fluid pressure in
strata below the area of unloading can become higher than petrostatic.
(2) Tectonic forces acting on a highly pressured formation might result
in fluid pressure above petrostatic lewvel. Fluid pressure above petro-
static level represents an unstable situation, and eventually the over-
burden would be fractured.6'15

Abnormal fluid pressures are usually observed in areas of very thick
sections of relatively young sediments and below a thick layer of imper-
meable material like shale, salt, anhydrite, limestone, or dolomite. When
the overlying beds represent an extremely effective seal, even very old
rocks can have retaihed very high fluid pressure. In Germany, in shale
beds of Permian age interbedded with Zechstein salt at the depth of 3150
m, a fluld pressure very close to petrostatic has been observed. In west
Texas, in a porous Permian dolomite at a depth of 960 m, A is equal to
0.89. A third example is reported from Argentina where tuffaceous mate-
rial of Triassic age at 2560 m of depth shows a A equal to O.7O.6')’L5

When highly pressured shales are exposed to sufficient pressure dif-
ferences flow will occur and diapiric shale structures similar to diapiric
salt structures can develop. If the porosity of the clayey sediments is
very high, their physical properties are much closer to those of a liquid,
such as molten lava, than to those of salt. In fact, examples are known
of clayey sediments flowing very rapidly or even producing pseudo-volcanic
phenomena.

The mudlumps of the Mississippi delta are small mud diapirs. The
conditions necessary to their formation are the accumulation of relatively

6.46

coarse sediments over a thick section of fine-grained materials. In
119

comparison to salt diapirism the process of mudlumps formation differs
only in the rate of evolution and the dimensions of the structures. Typi-
cal mudlumps are elongated in shape with a maximum length of a few hundred
meters. The time necessary for their formation is rather short. As a
matter of fact, there are zones of the Mississippi delta where the vari-
ations in water depth caused by the growth of mudlumps used to affect
navigation. The growth of mudlumps is not a continuous process but is
erratic and varied. On some mudlump islands, recurrent uplift exceeds

the rapid rate of destruction by wave action. The result is wave-planed
terraces and stepped islands. The highest rates of uplift coincide with
times of river flood and associated rapid sedimentation rates. Peak
growth rates of the order of a few meters per month seem quite possible,
while more normal rates of growth are of the order of a few meters per
year. Figure 6.6 shows the development of a family of Mississippi delta
mudlumps.

"Sedimentary volcanism'" is the term applied to the process by which
argillaceous unconsolidated sediments are extruded to the surface to form
pseudo-volcanic structures called mudévolcanoes. Mud-volcanism is con-
fined to areas where beds of highly pressured fine sediments are present.
Mud-volcanoes are found associated not only with oil and gas fields but
also with areas underlain by thick beds of weakly consolidated sand and
clay.6'u7’ 6.48 The extrusion of the mud always occurs along faults. The
energy necessary for the extrusion of the mud is furnished by the high
pressure of the fluids contained in the sediment pores. TFaulting is the
direct cause of the process, because it furnishes the channel through
which the abnormally high pressure can be released. The phenomenon 1s
basically different from diapirism. The mud flows very rapidly and be-
haves in all ways like a liquid.

Tn 1930 on the island of Trinidad there was a 400,000 cubic meter
mud flow; the extrusion lasted about 20 min.6'u7 In Erin Bay, Trinidad,
during November 3% and 4, 1911, the extrusion of about 250,000 cubic meters
of mud resulted in the formation of Mud-Volcano Island (known also as
Wilkey's Island). In these two cases the process was apparently spec-
tacular, because the descriptions mention the occurrence of explosions,

0. 49

flames, and even a 'mushroom cloud. Tn Erin Bay, in August 190k,
120

ORNL-DWG 70-6713

 

0 — AAAAAAANAANAANANANANAANINAIANA. MG L AAAAAAAN]

(o)

 
   
 

 

. PRODELTA CIAYS IWISSISSIPPI RIVER SOURCET]

RED AND GREEN CLAYS (EASTERN SOURCE)

 

 

S ALGAL REEF ZONE & ¢ 5 ¢

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.6 (a). Diagrammatic Representation of the Development of a

Mud-lump Family. MGL = mean ground level. Stages a-d. (From Morgan,
Coleman, and Gagliano.0.46)
121

ORNL-DWG 70-6714

 

NAAAAAAAAMANA. MG L

(e)

 

 

 

 

 

100 —1_. =

meters

150

 

 

 

200

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.6 (b). Diagrammatic Representation of the Development of¢ )¢
a Mud-lump Family. Stages e-h. (From Morgan, Coleman, and Gagliano. '

)
122

another mud extrusion of approximately 260,000 cubic meters resulted in

the formation of Chatham Island. In this case, large volumes of gas were

released also but no explosion is reported. Higgins and Saunders report ’
that a sample of gas from Chatham Island was found to be mostly
methane.6'5o The main force that caused the extrusion of the mud in v

these cases was probably the gas pressure; at any rate, the extrusions
occurred along lines of tectonic disturbance. The mud of Miocene age
reached the surface in a very plastic state and with a very high content
of water.

It is possible to conclude that argillaceous sediments can indeed
undergo extensive and even catastrophic deformation. However, the high
mobility is conditioned by the abnormal fluid pressure. It is therefore
clear that disposal of radioactive waste in a shale formation would be

acceptable only if the fluid pressure is at hydrostatic level.

6.4 Conclusions

Several mechanisms, which might result in the release of activity
from a disposal formation, have been reviewed in this chapter, although ’
the list is not exhaustive. We have considered several of the more likely
potential mechanisms as well as several unlikely mechanisms for activity
release, For the disposal formation all reasonable release mechanisms
should be analyzed and their probabilities and consequences assessed; in
many instances this exercise will likely require the collection of exten-
sive geologic data. The magnitude of the potential hazard that radioac-
tive waste presents for man and the environment is such that long-term
safety considerations must be given high priority in assessing the suit-
ability of any disposal method or formation. Although we feel that the
mechanisms discussed in this chapter are not likely to cause failure of
containment for a Jjudiciously sited waste repository, we believe that no
waste repository can be judiciously sited unless these mechanisms have
been considered in the evaluation of long-term safety. The most extensive
studies, to date, for ultimate disposal of high-level radioactive wastes
into geologic formations have related to disposal into salt. Careful *

attention must be given to geologic considerations in siting a disposal
123

facility in a bedded salt formation, and we feel that this should provide

assurance that subsequent inadvertent release of nongaseous radionuclides

from the formation will not occur.

6.1.

6.2.

6.3.

6.4,

6.5.

6.6.

6.7.

6.8.

6.9.

6.10.

6.11.

6.5 References

I. Halliday, "The Variation in the Frequency of Meteorite Impact
with Geographic Latitude," Meteoritics 2, 271-278 (196L).

M. J. 8. Innes, "The Use of Gravity Methods to Study the Under-
ground Structure and Impact Energy of Meteorite Craters," J.
Geophys. Res. 66, 2225-2239 (1961).

H. Brown, "The Density and Mass Distribution of Meteoritic Bodies
in the Neighborhood of the Earth's Orbit," J. Geophys. Res. 65,
1679-1683 (1960). o

G. S. Hawkins, "Impacts on the Earth and Moon," Nature 197, 781
(1963).

G. S. Hawkins, "Asteroidal Fragments," Astron. J. gg(s), 318-322
(1960).

W. K. Hartmann, "Terrestrial and Lunar Flux of Large Meteorities
in the Last Two Billion Years," Icarus 4, 157-165 (1965).

E. C. T. Chao, "Meteorite Impact, An Astrogeologic Phenomenon,"
Nuclear Geophysics, NAS-NRC, Publication 1075, pp. 219-232 (1963).
A. J. Cohen, "Fossil Meteorite Craters," Nuclear Geophysics, NAS-
NRC, Publication 1075, pp. 233-239 (1963).

A. Rittmann, Volcanoes and Their Activity, John Wiley & Sons, New
York, London, 1962. '

F. M. Bullard, Volcanoes in History, in Theory, in Eruption, Uni-
versity of Texas Press, 1962.

W. H. Bucher, "Cryptoexplosion Structures Caused from Without or
from Within the Earth? ('Astroblemes' or 'Geoblemes'?)," Am. J.
Sci. 261, 597-649 (1963).

R. 5. Dietz, "Cryptoexplosion Structures: A Discussion,” Am. J.

Sci. 261, 650-664 (1963).

e———
.15,

.1k,

.15,

. 16.

.17,

. 18.

.19.

. 20.

21,

.22,

.23,

.2k

12h

J. Goguel, "A Hypothesis on the Origin of the 'Cryptovolcanic
Structures' of the Central Platform of North America," Am. J. Sci.
261, 665-667 (1963).

B. A. Tkhostov, Initial Rock Pressures in Oil and Gas Deposits,
The MacMillan Co., New York, 1963.

 

M. V. Gzovskii, "The Geophysical Interpretation of Data on Young

and Recent Deep-Seated Tectonic Movements," in Recent Crustal Move-

 

ments, edited by I. P. Gerasimov and others, pp. 34-65, 1963.
(Translated from Russian, Program for Scientific Translations,
Jerusalem, 1967).

H. Borchert and R. O. Muir, Salt Deposits. The Origin, Metamor-

 

phism and Deformation of Evaporites, D. van Nostrand Co., Ltd.,
London, 196k.

J. M. Weller, "Compaction of Sediments," Bull. Am. Assoc. Petrol.
Geologists L3, 273-310 (1959).

H. D. Hedberg, "Gravitational Compaction of Clays and Shales,"
Am. J. Sci. 31, 241-287 (1936).

 

R. L. Bradshaw and W. C. McClain (eds.), Project Salt Vault: A

 

Demonstration of the Disposal of High Activity Solidified Wastes
in Underground Salt Mines, ORNL-4555 (1971).

 

F. W. Bates, R. R. Copeland, Jr., K. P. Dixon, "Geology of Avery
Island Salt Dome, Iberia Parish, Louisiana," Bull. Am. Assoc.

Petrol. Geologists 43, 9uk-957 (1959).

 

 

G. I. Atwater and M. J. Forman, "Nature of Growth of Southern
Loulisiana Salt Domes and Tts Effect on Petroleum Accumulation,"

Bull. Am. Assoc. Petrol. Geologists 43, 2592-2622 (1959).

 

M. Bornhauser, "Geology of Day Dome (Madison County, Texas)--A
Study of Salt Emplacement,” Bull. Am. Assoc. Petrol. Geologists
53, 1411-1420 (1969).

G. T. Atwater, "Gulf Coast Salt Dome Field Area," in Saline De-

 

posits, Geological Society of America, Special Paper No. 88, pp-
29-40, 1968.
F. Trusheim, "Mechanism of Salt Migration in Northern Germany,"

Bull. Am. Assoc. Petrol. Geologists 4, 1519-1540 (1960).

 
.25.

. 26.

.27.

.28.

.29.

. 30.

.51,

. 52.

.53,

.34

. 55.

. 36.

125

J. Bertroneu, "Les diapirs Triasiques du Bou Taleb Occidental,"
Geologie en Mijnbouw, Nieuwe Serie 19, 377-382 (1957).

J. V. Harrison, "The Geology of Some Salt-Plugs in Laristan
(Southern Persia)," The Quart. J. of the Geol. Soc. of London §é,
L63-522 (1930).

P. E. Kent, "Recent Studies of South Persian Salt Plugs," Bull.
Am. Assoc. Petrol. Geologists ig, 2951-2972 (1958).

D. Sannemann, "Salt-Stock Families in Northwestern Germany,"

in Diapirism and Diapirs, Memoir No. 8, Am. Assoc. Petrol. Geolo-
gists, pp. 261-270, 1968.

G. Dickinson, "Geological Aspects of Abnormal Reservoir Pressures
in Gulf Coast Louisiana," Bull. Am. Assoc. Petrol. Geologists 37,
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D. H. Kupfer, "Structure of Salt in Gulf Coast Domes," in First
Symposium on Salt, pp. 104-123, Northern Ohio Geological Society,
1963.

R. Balk, "Salt Structure of Jefferson Island Salt Dome, Iberia
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Geologists 37, 2455-2L7L (1953).

R. Balk, "Structure of Grand Saline Salt Dome, Van Zandt County
Texas," Bull. Am. Assoc. Petrol. Geologists 33, 1791-1829 (1949).
W. R. Muehlberger, "Internal Structure of the Grand Saline Salt
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of Investigation No. 38, The University of Texas, 1959.

W. C. Gussow, "Salt Diapirism: Importance of Temperature, and
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No. 8, pp. 16-52, American Association of Petroleum Geologists,
1968.

C. A. Burk, M. Ewing, J. L. Worzel, A. 0. Beall, Jr., W. A,
Berggren, D. Bukry, A. G. Fischer, and E. A. Pessagno, Jr.,
"Deep-Sea Drilling into the Challenger Knoll, Central Gulf of
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6.37.

6.38.

6.39.

6.40.

6.41.

6.4h2.

6.43.

6.414.

6.45.

6.46.

6.47.

126

W. R. Muehlberger and P. S. Clabaugh, "Internal Structure and
Petrofabrics of Gulf Coast Salt Domes,'" pp. 90-98 in Diapirism

and Diapirs, Memoir No. 8, American Association of Petroleum -
Geologists, 1968. .
F. E. Vaughan, "The Five Islands, Louisiana," Bull. Am. Assoc. .

 

Petrol. Geologists 9, 756-797 (1925).

R. W. Pairbridge, "The Changing Level of the Sea," Sci. Am. g_o_g(5),
70-79 (1960).

J. B. Wharton, Jr., "Jefferson Island Salt Dome, Iberia and Ver-

 

milion Parishes, Louisiana," Bull. Am. Assoc. Petrol. Geologists

37, b33-L43 (1953).
A. W. Musgrave and W. G. Hicks, "Outlining Shale Masses by Geo-

 

physical Methods," in Diapirism and Diapirs, Memoir No. 8, pp.

 

122-136, American Association of Petroleum Geologists, 1968.
J. A. Gilreath, "Electric-Log Characteristics of Diapiric Shale,"

in Diapirism and Diapirs, Memoir No. 8, pp. 137-14k4, American

 

Association of Petroleum Geologists, 1968. -
M. K. Hubbert and W. W. Rubey, "Role of Fluid Pressure in Mechanics

of Overthrust Faulting: Part I," Bull. Geol. Soc. Am. 70, 115-166 :
(1959).

W. W. Rubey and M. K. Hubbert, "Role of Fluid Pressure in Mechanics

 

 

of Overthrusting Faulting: Part II," Bull. Geol. Soc. Am. 70,
167-205 (1959).

J. H. M. A. Thomeer and J. A. Bottema, "Increasing Occurrence of
Abnormally High Reservoir Pressures in Boreholes, and Drilling
Problems Resulting Therefrom," Bull. Am. Assoc. Petrol. Geologists

45, 1721-1730 (1961).

 

J. P. Morgan, J. M. Coleman, and S. M. Gagliano, "Mudlumps:

Diapiric Structures in Mississippi Delta Sediments," in Diapirism

and Diapirs, Memoir No. 8, pp. 145-161, American Association of

Petroleum Geologists, 1968.
P. 5. Freeman, "Exposed Middle Tertiary Mud Diapirs and Related

!

Features in South Texas," in Diapirism and Diapirs, Memoir No. 8,

pp. 162-182, American Association of Petroleum Geologists, 1968.
127

©.48. A. V. Zuyev and A. A. Khrapov, "Minute Mud Volcanoes of the Gobi,"
Acad. Sci. USSR (Doklady) 186, TL-76 (1969).

6.49. R. Arnold and G. A. Macready, "Island-Forming Mud Volcano in Trini-
dad, British West Indies," Bull. Am. Assoc. Petrol. Geologists 40,
2748-2758 (1956).

6.50. G. E. Higgins and J. B. Saunders, "Report on 1964 Chatham Mud Is-
land, Erin Bay, Trinidad, West Indies," Bull. Am. Assoc. Petrol.
Geologists 51, 55-64 (1967).

 
128

7. SUMMARY AND CONCLUSIONS

High-level radicactive wastes generated by the reprocessing of spent
fuel elements in the projected nuclear power industry will require the
development of a comprehensive waste management program. The presence
259py (nalr-life, ’
Am (half-1life, 7340

years) requires assurance of waste containment for a time period of the

in these wastes of long-lived transuranics, especially

2,413 years), 2“0Pu (half-life, 6580 years), and k3

order of several hundreds of thousands of years. For such long time
periods only deep geologic formations offer the stability required for
preserving the necessary degree of containment.

Projections are made of the amounts of radioactive wastes accumu-
lated to the year 2020, assuming development of the nuclear industry in
accordance with Phase 3, Case 42, of the Systems Analysis Task Force,.

The Potential Hazard Index (PHI) is introduced as a means to evaluate
quantitatively the hazard associated with the existence of radioactive
nuclides. While the application of the PHI is somewhat limited, at the
present time, by the lack of data on the biological availability of
several critical nuclides once they have been dispersed into the environ-
ment and by the limited knowledge of the probability of wvarious mechanisms
of containment failure, the available information points to a few very
clear conclusions.

The risk associated with the inhalation of transuranics is several
orders of magnitude higher than the risk associated with their ingestion.

Permanent isolation in geologic formations is preferable to systems
in which later rehandling of the waste may be necessary. On the basis of
these considerations, it seems that the most prudent scheme of management
of these wastes involves solidification with final disposal into a suit-
able deep geologic formation.

The characteristics of products from various suggested solidifica-
tion processes are compared. IFor waste management considerations, the
most important characteristics are the thermal properties, the bulk
density, and the leachability of the products.

Interim storage will probably be required for some period of time

to allow for decay of the heat-generating rate of the waste product.
129

Interimlstorage facilities have not yet been designed in detail, but it

is reasonable that the eventual design will include provisions for cooling.
Accidental release of large amounts of radioactivity during interim stor-
age of refractory solids is less probable than if the waste is stored in
liquid form. 1In the unlikely event of permanent loss of cooling, the con-
tamination of groundwater would be prevented for a fairly long time period,
because the decay heat in the waste would evaporate all the water coming
in contact with the waste. Migration of radionuclides would also be re-
stricted by their interaction with soil minerals.

Many geologic factors must be considered in the selection of an ulti-
mate disposal formation, such as change in climate, change in hydrology,
erosion (channel and hillslope erosion, glacial erosion, etc.), tectonism
(orogeny, epeirogeny, subsidence, etc.), and volcanism. All these need
to be evaluated in addition to the rapid geological processes, such as
faulting, earthquakes, groundwater motion, etc., that are normally con-
sidered in the siting of nuclear facilities.

Even in a carefully selected disposal formation, the possibility of
accidents affecting the long-term containment of the critical radionu-
clides should be considered. Assuming (1) that the disposal formation
will be at least 300 m deep; (2) that all communications with the surface
will have been sealed; and (3), in the case of salt, that all cavities
will have been backfilled; the number of possible events which could re-
sult in activity from the waste reaching the biosphere is very limited.
They can be classified into two general groups: catastrophic events and
Slow geologic processes.

The catastrophic events capable of releasing activity from the buried
waste include (1) explosion of a nuclear weapon of sufficient power to
crater to the depth of disposal; (2) impact of a large meteorite, result-
ing in cratering to the depth of disposal; and (3) initiation of volcanic
activity at the site of disposal.

Some slow geologic processes potentially capable of causing a release
of activity from the disposal formation are: (1) faulting, (2) erosion,
(3) leaching and transport by groundwater, and (4) plastic deformation of
the disposal formation. The various processes can be combined to give a
series of release mechanisms, for which it might be necessary to evaluate

the order of probability.
130

The probability of the detonation of a nuclear weapon at the site
of disposal or of occurrence of minor errors, such as accidental drilling
through the disposal formation, is not considered.

The probability of impact of a meteorite large enough to crater to
the depth of %00 m is estimated to be on the order of 10_15/km2/year.
For a waste repository covering an area of 10 km2 the probability of be-
ing hit in a time period of 100,000 years is on the order of 10_7. This
value of the probability is apparently acceptable, seeing that nobody
seems to worry about such potentially catastrophic events. It should be
noted, however, that the impact of a giant meteorite might have direct
consequences much more serious than the exhumation of radiocactive waste,
at least from the point of view of short-term effects.

The evaluation of the probability of the other geologic processes
listed above cannot be based on the assumption of random distribution
and would only be possible for specific sites. An accurate knowledge of
the regional geology would be essential. Hence, the considerations dis-
cussed in this report cannot result in a numeric estimate of the proba-
bility of occurrence, but they may provide a guide with respect to
information that must be obtained if the risk has to be minimized.

The preceding considerations seem to justify several conclusions.
Conversion of waste to solid form results in a reduction of risk during
the interim storage period and is indispensable for the transport of the
waste to the site of ultimate disposal. However, the physico-chemical
characteristics of the solidified waste may have only a minor influence
on possible consequences of accidents during the interim storage and
especially after disposal in the geologic formation. This is only true
1f the possible release mechanisms are: (1) atmospheric release of vola-
tile components and (2) transport of the nonvolatile components by ground-
water through geologic materials characterized by low permeability and
high ion exchange capacity.

In case the geologic materials surrounding the waste do not provide
an effective barrier to the movement of radionuclides, the leachability
of the solidified waste might become the parameter controlling the mo-
bility of the nuclides, but this situation should be prevented by siting

storage and disposal facilities in suitable geologic environments. For
151

the interim storage facility the geologic requirements are essentially
limited to: (1) tectonic stability of the area and (2) low permeability
and high ion exchange capacity of geologic materials surrounding the
waste.

For the ultimate disposal formation, in consideration of the long
containment time required, much more stringent geologic specifications
must be met. |

In the selection of the ultimate disposal formation, the following
criteria should be used. The disposal formation should be plastic enough
to cause sealing of fractures in a fairly short time but not so plastic
as to permit the occurrence of diapiric processes in a time period of
several hundred thousand years. There must be no circulating groundwater
present in the disposal formation, and the geologic barriers between the
disposal formation and the closest aquifer should be adequate to withstand
possible geologic proceéses, such as faulting. Depth of burial should not
be reduced excessively by erosion of the land. Therefore areas character-
ized by high rates of erosion should be avoided. The possibility of future
increase in erosion rates because of uplift of the area, climatic changes,
or action of man should be considered. Finally, the disposal site should
be located in an area distant from orogenic belts, tectonically stable,
and without records of volcanic activity in the last few million years.

A geologic formation selected with these criteria would offer an
extremely low risk of radionuclide release. If the unpredicted should
happen and containment fail, groundwater would be the most likely medium
of activity transport. With groundwater as medium acting to dissolve and
transport the waste residues, the global risk for mankind would be effec-
tively limited because: (1) movement of plutonium and americium through
ion.exchanging geologic materials is a slow process; (2) the most likely
mode of intake of plutonium and americium from an aqueous environment is
by ingestion, and their PHI's‘by ingestion are three to four orders of
magnitude lower than their PHI's by inhalation. Finally, it must be con-
sidered that for plutonium and americium in contaminated water, the criti-
cal pathway is by direct ingestion of the water, because their mobility
along food chains is very limited, and to date, no significant reconcen-

tration mechanisms have been reported for these nuclides.
132

APPENDIX A

ESTIMATES OF RADIONUCLIDE MOVEMENT THROUGH THE GROUND

Predictions of the rates and extent of movement of radionuclides
through the ground can be made if the pattern and rate of groundwater
movement and dispersion can be adequately described, and remains rela-
tively constant with time, and if the nature and the degree of interaction
of radionuclides with the solid matrix can be described. Fluctuations
in both groundwater movement and solute interactions occur over rather
short periods of time, so that it is rather presumptuous to expect that
predictions of behavior extending thousands of years into the future
will provide a realistic picture. It 1s ordinarily assumed in such cal-
culations that the solid phase is immobile, and for short-term periods
of movement this is an acceptable assumption; however, for very long
periods the degree of translocation, especially of fine particles, may
contribute significantly to the total movement. In spite of the obvious
shortcomings of such exercises, they do provide some benefit, because
they allow us to make general observations regarding the relative extents
of movement that could be anticipated.

For our purposes, we have assumed that groundwater would move longi-
tudinally and unidirectionally through the ground. No lateral or vertical
dispersion was considered, but longitudinal spread of the solute is
assumed to occur. We further assume that the interaction of the radio-
nuclides with the earth material is principally ion exchange and that
the transport of activity through the formation can be.described by
Glueckauf's model.A'l A listing of computer programs, FPDSCILS and
FPISOILS, based on this mode are given in Tables A.1 and A.2. Comment
cards are included that describe the input.

For the transport of activity through the ground, assumptions were
made that correspond to the properties of Conasauga shale. Conasauga
shale has a mean ion exchange capacity of 11 = 1 meq/lOO g. The ground-
water 1s similar in composition to Clinch River water, which has a total
cation concentration of about 0.002 meq/ml, primarily calcium and mag-

nesium. A mean groundwater velocity of 20 cm/day and an effective plate
vy

Tr»rfirveh

133

Table A.1 Listing of Program FPDSOILS

“TNsLyMyE.
PROGRAM FPDSOILS
TPROGRAM T DEPICT THL DISTRIBUTICON OF RAUICNUCLIDES IN THt GROUND
AS A FUNCTION 0F DISTANCE
TTTUDIMENSION TITLE(20),HLL1C) yDCLLO) 9A(L0) 3 T(500),CALLO)»Y{(10),
LYP{S00) s X{5C0)yDKIL10)4D(500),43{10)
TTIMPLICHIT REAL%B(A-HY ,REAL*¥3(C-2)
111 READ (50,100) (TITLE(I),1 = 1,20)
TT{O0 FORMAT (20a4) - '
PRINT 6
7T 6 FORMAT (11 30X40HTIME AND SPATIAL DISTRIBLTION UF FISSION
118H PROLUCTS IN' SOILS///)
TUUPRINT By (TITLE(T), T = 1,201
8 FURMAT {1HO20X20A4%)
TTTTTITREAD 2, FACTOR, TLEAKy VoC y CCWHPLHT
C FACTOR IS THE WEIGHT UOF SUIL CONTACTEC BY UNE ML GF SULUTIOGN IN G/ML
C TLEAK IS THE DURATION OF LEAKAGE IN YEARS ' ’ ‘
C V IS THE GROUNDWATER VELOCITY IN METERS PER CAY
C C IS THE SALT CONCENTRATICN OF THE LEAKING WASTE SULUTIUN
C CGW IS THE SALT CONCENTRATIUN OF THE GRCUNDWATER IN MEQW/ML
CPUAT TS THE THEORETICAL PLATE HEIGHT IN METERS o
2 FORMAT(7F10.0)
CN = 365.%TLEAK
 PRINT 4, FACTOR,ONyV4CyCGWsPLHT -
4 FORMAT {114 1OX17THCUNTACT FACTOR = F10.3/1CX19HDURATIUN OF LEAK =
 1F10.2,4HDAYS/10X23HCROUNDWATER VELCCITY = F10.3,10HMETERS/DAY/
TTTU210X22HWASTE CONCENTRATICN = F10.3/710X23HGRCUNUAATER CONCENTRATI
35HON = F10.5/10X27HTHEQORETICAL PLATE HEIGKT = F10.3,6HMETERS//)
READ INPUT TAPE 50474KT o (T(I)yI = 1,KT) ‘ '
C KT IS THE NUMBER OF TIMtb CONSIDERED
C T(I) IS THE TIME OF TRAVEL IN YEARS

7 _FORMAT (I119/{8F10.0))

TTREAD 330y (ACI),B(I) yDCUTYDK(I) yHLIT) yCA(TI) 91 = 14L)

C L IS THE NUMBER OF RADIONUCLIDES CONSIDERED
C A(I) IS THE IDENTITY OF THE RADICNUCLIDES
C HL{I) IS HE HALF LIFE OF THE RAGIONUCLIDE IN YEARS
C DCCI) 1S THE SOIL KD FOR THE RADIONUCLIDE IN THE LEAKING SOLUTION IN ML/G
C DKUI) IS THE SOIL KD FOR THE RADIGNUCLIDE IN THE GRUUNUDWATER IN ML/G
CCA(IY IS THE DRIGINAL CONCENTRATION OF THE RACICNUCLIDE IN THE LEAKING SOLUTIQ

3 _FORMAT (I1/{2A44,F12.047F10.04£10.2))

READ 727+DINITsJAsDAyJBsCByJCyOMyJDyDDyJESDEsJF 9 DF 3 JGy DG
C DINIT IS THE INITIAL DISTANCE CUNSIDERED IN METERS

L
'T"l

C DA,DB, ETC. ARE INCREMENTAL INCREASES IN METERS
C JA,JB,ETC., ARE THE NUMBER OF INCREMENTAL DISTANCES CUNSIDERED ‘
T27 FORMAT (F10.0913F 70913 3FT7a00134F700134F7.0913,FT20,13,F7.0

113,F7.C) e

JJ = JA ¥ JB+ JCH+JO+JE+JIF+IG
. XF tJJ - 500) 199941999,1598
1998 JJ = 500
1999 DELD = CA S e

STST = G INTT e e e e et e e e

V = 365.%V

DO 200 J = 1,

C THIS LOOP CALCULATES BEHAVIOR OF EACH RADIONUCLIDE

AQ = V/PLHT/{DCUJI*FACTOR)

BQ = V/PLHT/(DK(J)*FACTOR)

7 =0 TAGIIS7HLTT)

 
134

PRINT 59A¢4)y8{J),DCLUY) s DKIJ)sHLUY) yCA(J)

. 5 FORMAT (UM /7 //5XY6HACTIVITY DUE TU 2A4/5X13HDISTRIBUTIUN
ZBbHCUtFPICIcNT R LEAKING SOLUTION = F1lO.4/5XLZHDISTRIBUTIGN
330HCOEFFICIENT FUR GROUNCWATER = F10.4/5X12HHALF LIFE = F10.3,
45HYEARS/SX3IHINITIAL ACTIVITY IN LEAKING SOLUTIUN = E20.8/77)

IT = 0.0

DU 3C0 K=1,KT

C.THIS LGUP CALCULATLES THE BEHAVIUR FUOR EACH CESIGNATED TiMt

PRINT 41,T(K)
41 FORMAT (1H 45X15HTIME ELAFSED = F15.445HYEARS//5X
L114HDISTANCE(M) 10X14HACTIVITY LEVEL7X21HLOG Ut ACTIVITY LEVEL
27X12HSOIL LOADING 9X16HLGG SOIL LOADING/)
70 TIM = T(K)
_ 12 DEC = Z*TIM
IF(DEC + 50.) 300 300937
37 IF(TIM - TLEAK) 9,9,10

9 AM = TIM®AQ

 

10 AMP = (TIM-TLEAK) =By
AM = TLEAKXAQ +(TIM-TLEAK)*BQ

T AL T ek TEWR T R AP N T

BMP = (TIM ~ T FAK)*V/PLHT
11 DINIT = DIST e

BM = TIMXV/PLHT

 

o KK= 00
DINIT = DIST
DELD = DA

T THIS LOOP CALCULATES THE BEHAVIOR FOR EACH LISTANCL SPECIFIED
_..D0 208 I = 14JJ
KK = KK + 1
. bti) = DINIT -
AN = DI{I)/PLHT
ow_DINIT = DINIT + DELD
XARG={AN-AM) /{SQRT(2.0%AM))
23 CALL NPOA {XARG,~1,0RD,AREA,ERR)
IF(XARG) 553,554,554
__ 253 AREA = —AREA , o
€54 Y{I) = (1.0-AREA)}/2.
_ IF (AN = 10.) 402,402,403
402 XARG = UAN+AM V7 (SQRT(2.G+AM1Y "
CALL NPOA (XARGy—1,0RDyAREA,ERR)
BAR = (1.0-AREA)*(EXP(2.0%AN)/2.)
_ . Y{I1) = Y(Ii1+BAR o o
403 X(1) Y(I) T
555 IF(T(K) -~ TLEAK) 538,538,537
537 XARG = (AN-AMPI/{SQRT(Z.0%AMPY)
___33 CALL NPOA (XARGy—1,0RDsAREA,ERR)
CIF(XARG) 590,4591,591
560 AREA = —AREA
591 YP(I) = (1.0 = AREAY/2. 7
IF (AN - 10.) 404,404,598
404 XARG = (ANFAMPY/USQRTUZ2TC*AMPY Yy
_____CALL NPUA (XAKGy—1,0RDyAREA,ERR)
BAR = (1.,0- ARLA)*TEX?(? O*%AN)/2.)
YP(I) = YP(I) + BAR
598 X(1) = ABS(Y(II=YP(IN)
538 IF(X(I) - 1.0F=-50)208,208,92

92 XARG = (AN-BMI7Z7({SQRT(2.0%eM T

 

 

 

 

 

 

 

 
e

135

TCALL NPUA (XARG,—~1,0RD,AREA,ERR)Y
_IF(XARG)BU0,801,801
TEOO ARERT=TAREA T
801 YP(I) = (1.0-AREA)/2.
IF (AN - 10.,) 405,405,406
405 XARG = (AN+BM )/ (SQRT{2.C*BM ))
TTTTUCALL NPUA (XARGy-LsORDyAREASERRY
BAR = (1.0-AREA)*(EXP{2.0%AN)/2.)
TTTTUNP(TY =TYPLLY O+ BAR -
406 IF(TIM -TLEAK)330,830,831
830 Y(I) = 0.0
GO TO 832
831 XARG = (AN-BMP)Y/(SQRT(2.0%BMPY)Y
CALL NPOA (XARG;—1,0RD, AREAyERR) _
e TRRRE T 7605 10 12701 R
_ 700 AREA= -AREA
701 Y{I) = (1.0-AREAY/Z2.
IF (AN — 10.) 407,407,832
THCT TXARG = {(AN+BMP)/(SQURT{Z2.0%BMPY)
CALL NPUA {(XAKRGy—~1,0RDyAREA,ERR)
TTTTTTBAR TETUTLO-AREAYRIEXPI2 JOXANY /20 T T T
Y{I) = Y({I)+BAR

 

832 Y(1) = ABS(YP{I)-Y(I))
CQ=CALIIEXTT)I*DCIJI*(EXP (DEC))

TXXEXTDIRCACO (Y (DI+ (L. -Y(INI=DC (I /DKy (EXP(DECY)

XLW = 0.43429%ALOG(Q)

e O A SR ATBETRE) e

 PRINT 19,D(1)sXXsXLX,Q9XLAQ

19 FORMAT (IH F20.3,4XE20.3,9XF10.5,11XE20.3,9XF10.5)

CIF(KK-JA}1012,1012,1000

1012 DELD ="DA
G0 _T0 208 N

000 TFIRK-JA~U8)1001,1001,1062

1001 DELD = DB
60 TO 2¢8

1002 IF(KK-JA-JB-JC)1003,1003,1004

1003 OELD = DM

O TO 208 o i s s
1004 TFIKK=JA<IB=JC=J011005,1005,1006 7 7777w o
1005 DELD = DD

GU TO 208
1006 IF(KK-JA-JB-JC-JD-JE)10C7,1007,1008

 

1007 DELD = DE
GO TO 208

 

TO08 TFIRK= A= T8 JE-J0=IE=IFY ™ 16097 1009, 1016~

1009 BELD = DF e

GO TO 208
1010 DELD = DG

 

208 CONTINUE
300 CONTINUE

 

 

200 CONTINUE
GO 10 111
END
136

SUBROUTINE NPUA (XARG,ITYPE,ORC,AREA,ERR)
IMPLICIT REAL®3{A~H) JREAL*8(C~-2)
€ €3 UCSD NPUA
IF (IARS (ITYPE)-6)T7,47416
LT ERR=ABS (XARG)
AREA=0.0
e IFLITYPE)9,1648
8  ERR=0.707T106781%ERR
9. KIYPE=1ABS (ITYPE)
IF((ERK*%2)~88.028)15,15,10
10 ORD=0.0 B
IF(IABS (ITYPE)<6)11,17,11
1l AREA=1.0
G0 T0 19
15  URD=1.12837917%EXP {=(ERR%*%2))
IF(IABS (ITYPE)=6)12,6412
12 ARFEA=1.0/(1.C+0.3275911%ERR)
AREA=L .0~ (({(0.9406460T*AREA=1.287822453) %AREA+L.259069513)
e JEAREA-0.252128668) %AREA+0,225836846) XAREAORD
19 GO TO (6924344,5) KT YPE

R S e LT

2 . __AREA=AREA/2.0 .
GO TQ 6

3 _AREA=1.0-AREA
G TO A

4 AREA={1.0-AREA})/2.0
GO TO 6

.5  AREA=(1.0+AREA)/ 2.0

6 IF(ITYPE)1T7,16,14

14 ORD=0.3535533305%0RD
17 ERK=0.0
e OO TO L8
16  ERR=1.0
18 _RETURN
END
137

Table A.2 Listing of Program FPTSOILS

*KXFTWel of o
PROIGRAM SPTSCILS
TEEAREENTTG CEPICT THE ANVEMENT OF RADTONUCLINES IN THE GROUND AS A
FUNCTIGN OF TIMF
EACTAR 1S THE WETGHT OF SOTL CONTACTED BY ONF ML DF SCTUTION IN G/ML
TYPICAL VALUES OF FACTOF RANGE FROM & TO B
ATTOR = TRULK UENSTTYTZ70PCROSTITY Y TR (GRAIN DENSTTY)I(] - POROSITY)I/PORNSIT
TLEAK IS THE DURATION OF LFAKAGE IN YEAFS
TVTS TEE GROINDWATERVYELACTTY "IN METERS PFR DAY &
C (RFAL DISTENGCF OF TRAVCL DIVIDED BY THE TRAVEL TIMF)
C C 1S THE SALT CONCENTRATION DF THE TELZXING STLUTYION IN MEQ/ML
C CGW IS THE SALT CCHNCFNTRATIOCN OF THE GFCUNDWATER IN MEQ/ML
T PLHT 1S THE THEORETICAL PLATE HFIGHT IN METERS
C TYPICAL VALUFS OF PLHT RANGE FROM 1 TA 20 METERS. VALUES DEPEMD O
T TTHE ITTOMOSENEITY 98 THE FORMATION AND GROUNDWATER VELACITY
C FOR DOWNAARD PERCCLATION INTL A SGIL CKR FOR A LABORATORY COLUMN
T VALUFS MAY BF ON THE DRDFPR ©F A FEW CENTIMETERS ‘
C D IS THE DISTANCE 71F TRAVEL IN METFRS

 

 

O ol oo Ho

 

T 2 IS THEINENTITY OF THF RACTCNUCLICE
C HL IS THF HALLF LIFE OF THE RAPIONUCLI“F IN YFARS
THETTS FHE SOILKA FNR THE FADTCNUCLIDS IN THE LEAKING SOLUTION IN ML/G
C DK IS THF SOIL KD FOR THE RADIONUCLINS IN GPOUNDWATER IN ML/G
T MEASURED VALDTS AFZ 2EST FOR THE KO BUT THEY CAN BE ESTIMATED KMNIWING THE
C CHEMISTRY CF THF SNLUTICONS AND THE MINERALOGY OF THE FORMATICN
T C2 IS5 THE AIGINZL TONCENTRATION OF THE RADIONUCLIDE
TMPLICTT REAL#R (A=), REAL¥R{O-Z)
T TME RS TUN TITLE(Z2T )y HL(IC),,DCHYIN) L AL, TUSOR)LCALIG), Y520,
L YPUSCS) o X(500) JCSALT{BCC) s XLXI50C),DK10),8(1C)
TITL READ (5C,1CH) (TITLE(IY. 1T = 1,2C)
100 FORMAT (202<)

TN

6)IFURMAT(1HT 3(x 4%HTIME AND SPATIAL DISTPIBUTION OF FISSIaN
T T Y aH PROILCTS CIN StILCIII)‘”

PRINT B, (TITLE(I),T = 1,20)
TROFORMAT (VHCOACX20A4Y
1 READ ?vr'\rTqKOTLF‘K Vv 9(GW¢PLHTQD
‘,7 tf‘JR‘AbT(" Fi* ) o ’ T o

IF{TLEAK - ‘.)acco.angu.«oo
TECOC DN ETEEE UETLEART T
PRIMT 3C U4 FACTUR DNV VLC, CGW,PLHT D
2006 FORMAT (TH TAXTTHCONTACT FACTOR = FI1D,7/TCXIGHDURATION NF LEAK
1F10e2+4BBAYS/ IO X2 3IHGRNOUNDHWATER VELOCITY = F1042+14HMETFRS PFR nAY/
T T OX 2 2 HWASYE CONCENTRATTION = FICL37T0X23HGROUNTWATER CONCENTRATI
A5H0ON = F1Ge5/1CX27HTHE HPET{CAL PLATE HEIGHT = F10.3/ 10X
e AT TS TN E T T T SURFACY RETER =T F1IN TV BHMETFRS /7Y ‘
GN TN 35032
TEGCY TN =ETTURRK T
30GC7 PRINT 4o FACTCRsDMyVoC o GWo PLHT LD
4 EORMAT (TH IOXLTHCONTACT FACTOR = FIOJTZYCXISHDURATION DF LEAK =777 77
1F1042,4HYRS /10X23HGP OUNDWATER VELOCITY = F10e?414HMETEFRS PER DAY/
TR 2 WA STE CUNTENTEENTIDON = FYC I/ TOXZIHGINUNDWATER "TONCENTRATT
35HON = Fl0eS5/10X27HTHENPRETICAL PLATE HFIGHT = F10.3/ 10X
T A OBADISTANCE IO SURFACE WATER = Fl0.3,.6HMETERS/7Y oo
DN = 3565 4%TLFAK
YO0 READ L TINIT, TA DA, TR, DB, IC, M, ID, D, IF,DE, IGDFVTH,DG
7 FORMAT (FIC.C.I2, FT.UyI?.F7.JqI:.F’.O,IE,FY.OvI'.F? 0413 .F? 3
IT3.F7.0) s T "

 

 

 

 

rae; o

 
138

 

T DnE T = DA
KT = I4+IP+I'+II+I +IG+IH .
- “TFT(K T Y)Y PTGy e, 2ecy o T T ' T
2061 KT = 5!
2000 TT = TI.\iIT T . T ' .
Rr“)?,L.(A(I),B(I),I‘C(IJ'DK(I).HL(I).F'\(I).I =",L) y

T RIRMAT (11T /0ZAS,FI T OT10.CLEL0.2 )
AN = N/PLHT
A | L L A .
R 20 J = 1L
TTTTUURELY = AR T T T
A = V/FLHT/(14C # OC(I*FEACTOR)
TTTTTURY = VJPLHT/Z{VSN ¥ TROJIEFACTORY 0 T
7 = =N.e3215/HLLJ)
TPRINT R yATI) v B ZBCT IS TRTIVVHL U)W CA(IT
5 FEIMAT (IH ///5X16HACTIVITY DUE TN 284,/5X13HDISTR IBUTION
T TIISHCOEFFICTEMNT FOR LEAKING SCLUTION = F1U.4/5XIPHCISTRIBUTION
23CACOEFFICIELT FOR GRNUNLWATFR = F10.4/5X12HHALF LIFE = F10.3,
TUOSHYEATS/SX T T ‘
33HINITIAL ACTIVITY IN LEAKING SOLUTIGH = £20,8//13X11IHTIME (YEARS)
T EXLSHAC T IVETY LEVELY ZX1SHLOG ACTIVITY LEVFLSXAHSALT
514H CONCENTRATIANEXUSHFPACTION LGST /)
TUUTETUAN S de ) ACDB V0T .AC0T
3007 X0 = 040
TGO TTg Al T
3005 X9 = FX (2 CRANY /2.
ICAETXINC =",y o o
KK = O
COTINIT = TY
XOX = 040

Wl

KK = KK + 1
e T TR TR SR T T o e
TINIT = T(K)

IF(DEC + 454) &00 400,37
TR TTE{TO-TLFAK )Y 2,81 7 e e
S AM = T{K)#AD
e Ly I
1¢ AM = TLEAK¥AQ+(T(K)=TLFAK)*RQ
I XERG = (AN = AMY/SART(2JCEAMY T e
23 CALL NPCA (XARG.=1+0RD,ARFA, EXR)
w"'fi:‘(‘x]}‘?fg !\"'_‘g' ’E",' 15'57, T T e meeT T e s e
£53 AREA= =ARFA
55 YR = T OSAREAY 7w
XARG = (AN + AM)/SORT{2+C%AM)
AT NPT UXARG=T3TIRD AREA, ERR ™~ 7 e
BAR = (1.0 - AREA) * X0O
XTRT = YIKT# BTR
555 IF (T(K) - TLFAK) 538,537,537
TP T (KT TTE AR #R O A
XARG = (AN - AAP)/SQRT(Z CHAMP)
I AL NP A T TXARG y= T TR BRE A ERR T 77 mm s o o simims imms s e
IE(XARG) 590,591,591
TG0 AREA = —ARFA
591 YP(K) = (leC =~ AREA)/2,
ARG T TRI 5 AT 7 SORT 3 2 QR ot reemermimmms e e e e o

 

 

 

 

 

CETACN K=1.KT . el i : -

»
139

T UCALL NPOA IXARG,=1,0RTVARFA,FRR) -
o BAR = {1.0 ~ AREA) * XNQ

563

TEER
TTED

o2

396
gal

Ty Sy

822

811

RAR = (V,T = AREA) * XNQ™ o
YP(K) = YP(K)+BAR

CIF({TIK) = TLEAK) E30,583G,831
Y(K) = Co(
GO T 3322 o
BMP =(T({K)=TLEAK)*®V/PLHT
XARG = (AN = BMF)/SQRT(2.CHBYP)
IF(XARG)Y TCr,7ci, 7oy
AREA ~ARFA

7¢O

2c®

TBM = TOKIHFV/BLHT

YPIKY = YRP(K) '+ BaR

X(K) = Y(K) = YP(K)

CONTTIHNUE

IFIX(K) = 1eGE=2C) 820,620,790

XAKG = (AN = BM)I/SQRT(?.C¥BM)

CCALL NPUA (XARG,=1,0RD,AREA,ERR)

IF (XAP3) 8C0,BC1,RNY

AREA = —AREA
YP(K) = (1.0-ARFA)/Z.

XARG = (AN + BM)/SART (72 ,0%BM)

YK = (1=FreAy/a.
ARG (AN + BMP)/SORTI(2.C*BMP)
CALL WNPEHA (XARG =1, 0RDJARE A, ERR)

RAR = {1.0 = ARFEA) * XNOQ

Wonin

Y(K) = YP(K) = Y(K) = RAR

CSALT(K) = Y{K)*¥(C = CGW) + CGW

XOX = XOX +((XBX + X(K)V*DELT/24)/CA(J)/TLEAK

 

0?2C

Canl

1013 IF(KK - IA) 1012.,1712,10C0C
T‘fl"" T Z’-’—T‘)‘?m%?{_‘;x‘v"n‘h' T T LT LT

XBX =EXAIKY T

TE(X(K) = 1.0E-12)1612,1C12,401
XLX{K) = €437 AL0G(XIKY)Y

CPRINT 184 T(K) ¢ X{(K) o XLXCK) yCSALT{K]) 4 XQX
TR FCRMAT (TH RIS 4 XEY1C (B BXFIG 2, 6XF19.5+5XE19,4)

G3 TO 430

 

1006
1Go1

IF (KK - TA = TRY 1oct,1ecl,1002

DELT = 0B

 

1062

 

TCCR

105

 

 

1036

 

AU

X{K) = XU =CATIN H(VIK)+{TC=Y(R)IXDC L) /0K (I ) )V*EXPIDET)

 

GO T «CC N T
TF{KK-12-IB-1C) 1003,1C02,1004
DELY = DM o T o e Tt
GO TO 409
10C4 TF(KK=-TA-TB-1C-1D) 1ICC%,1TC05,1G06 -
DELT = DD
GO T0O 4290 - - T . -
IF(KK=TA=IB=TIC~ID=IF) 10OCT,10G07,1N08
SETT S TF s I N ——— el e
GO TO 400
1008 TF(KK=TZ=TB=TC-TD-TE=-IG) TCT9,1C0S,T0I0 -
1009 DELT = NF

UL ToRooy T

1010
“CU

DELT = DG
CONTINUE
140

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

END

IO CORTINGE T e e T - -
GO Ta 111 .
o L e
— e o
»
N SURROUTINE NPLA (XAPG, ITYFE,DRD,AREA, ERR)
TTTTIMPLICT T REAUHC(A-HYVREALES(G=~2y ~
C3 UCSD NFNA
I[F (1288 (ITYPFI=6YT, 741 7 =
7 ERR=ABS ( XARG)
AR e )
IF(ITYPE)C 1648
- R I T CE RV RE R o o e
KTYPE=143S (ITYPF)
[F((ERR®%Z)=FRN2B) 15,415,106 T A
10 ORD=C.0
T U IF(IARS UITYPEY-eYIV AT T R - i -
11 AREA=1,D
TS e e et e mrmeeere e )
15 JRD=141293791 7#FXP (= (FRE*%2))
T T E(IABS (ITYPE)Y-EN1D,6,1e T T
12 ARFA=140/(1.04063275G611%ERR)
AREA=T . O={{{(C.SuCh4bU7T*AREA=T 28782245 3V (¥ARFA+1.25%665131 .
L¥ARFA=3. 252128668 ) ¥ARFA+( , 225836846 ) ¥ ARFAXORD
19 GO 10 (5+253,445) KTYPE T T -
2 AREA=AREA/2.0.
GO T0 e T - T e -
3 ARFA=1,0-ARFA
GU To &5 T T T .
4 AREA=(1e0=AREA) /241 :
T - - e e et i e i
6 IFCITYPE)I T, 16,14 - T T T T
14 0’D=0,3535532905%0RN" *
17 ERR =0, T T T T o - -
GN TO 113
1% FETT e e S e e e . .
18 RETURN
141

height of 15 m were assumed, based on field measurements at the Oak Ridge
National Laboratory. The porosity of the shale effectively contacted by
solution is assumed to be 25% with a grain density of 2.65 g/cmB. Waste
composition No. 3 from Table 3.2 was used for estimating stable ion con-
centrations of the leachate. For liquid waste the total concentration
was used. It was assumed that for solid product all of the acid would
be volatilized, and that for spray melt and glass products other stable
solids would be added. The composition of the leachate was estimated by
assuming that all ions would leach from the solids at a uniform rate.

In the case of cesium exchange it was assumed that Conasauga shale
has 0.01 meq/g of its exchange sites highly selective for cesium.A'2 The
cesium to stable ion selectivity coefficient for these sites was estimated
to be 10,000. The remaining exchange sites were assumed to be nonselec-
tive. Using a stable ion concentration of 7.92 meg/ml and a cesium con-
centration of 0.057, we can estimate the equilibrium cesium loading and,
hence, the cesium Kd for the waste solution. For the exchange sites that
are highly selective for cesium we solve the selectivity coefficient

equation:

Js  m

qm CCs

Using the values assumed above:

K =

Us 7.92
0.01 - q,, = 0.057 '

 

10,000 =
Solving for Uog for these sites gives:

Qg = 0.00986 meqg/g .

For the nonselective sites:

s 7.92
0.1 - q'ng ~ 0-057 ’

 

This yields an additional loading of 0.00071 for the nonselective sites.
The total loading would then be 0.0106 meg/g, and the cesium K, would be
this loading divided by the cesium concentration, or 0.19 ml/g. Similar

estimates can be made for each of the leachates and for groundwater.
142

Estimates for strontium exchange were made by assuming that there

A.3

is no selectivity for its adsorption. Those for plutonium and ameri-

cium were estimated based on the work of Hajek.A'LL A summary of the K

 

 

 

d
values used is given in Table A.3.
Table A.3. Summary of K4 Values Used in
Calculating Radionuclide Movement
K4(ml/g)
9OSr 15708 259Pu 2L”'Am
Liquid waste 0.011 0.19 0.87 0.007
Leachate from pot calcination 0.2k 0.85 17 0.12
product
Leachate from spray melt L0 430 2,500 21
product
Leachate from glass 53 5,700 5,500 27
Groundwater 55 10,000 3,450 28

 

We then assume that a can of waste 28 cm in diameter and 300 cm in
length is ruptured and the contents come into contact with percolating
groundwater. Although we mentioned earlier that the heat-generation rate
would cause evaporation of all inward percolating groundwater for some
time, we are tacitly assuming here that the heat-generation rate has de-
clined sufficiently so that grouhdwater percolation does occur. Liguid
waste would take about 6 days to percolate into Conasauga shale, and about
100 days would be required for enough groundwater flow for complete dis-
solution of a container of calcined waste (assuming a leach rate of 0.5
g/cm?/day). The other solid products would take much longer, on the order
of 750 to 800 years for the spray melt product (at lO—LL g/cm?/day) and
proportionately longer when the leach rate is smaller.

Typical outputs of calculations are listed in Tables A.L4 and A.S.
Results from a number of sets of calculations were shown in Figs. L.1 to

L.k,
Table A.L4 Output of Program FPDSOILS

TIME AND SPATIAL DISTRIBUTICN OF FISSION PRODUCTS

IN

SOILS

 

 

LIQUID RELEASE
CONTALT FACTOR = 7.950

 

DURATICN OF LEAK = 5.48D4A

GROUNDWATER VELDCITY =

YS

0. 200METERS /DAY

 

 

WASTE CONCENTRATIUN = {925
GROUNDWATER CONCENTRATION = J.00200
THEORETICAL PLATE HEIGHT = 15.00CMETERS

 

 

 

ACTIVITY DUE TO SR 90

DISTRIBUTICN COEFFICIENT FOR LEAKING SOLUTICN

DISTRIBUTIONCOEFFICIENT FOR GROUNDWA
HALF LIFE = 28.000YEARS
INITIAL ACTIVITY IN LEAKING SOLUTICN

TER =

G.0110

0.32600C600D 05

TIME ELAPSELC =

0.0150YEARS

 

DISTANCE(M)

ACTIVITY LEVEL

LOG_OF ACTIVITY LEVEL

_SOIL LOADING

 

_LOG_SOIL LOADING

 

 

 

 

 

 

 

 

 

0.0 0.3260 05 4.51301 0.358D 03 2.55442
1. 000 0.274D 05 4,43837 0.353D 03 T 2454775
2.000 0.2210 05 4.34517 0.347D 03 2.54010
3.000 0.1710 05 4.23209 0.340D 03 TT2.53141
4.000 0.125D0 05 4.,09800 0.332D 03 2.52164
5.000 0.875D 04 3.94195 0.3240703 2.51071
6.000 0.580D0 04 3.76313 0.315D 03 2.49859
7.000 0.364C 04 3.56089 0.306D 03 2.48522
8.000 0.216D 04 3.33473 0.296D 03 2.47055
9.000 0.121D 04 3,08431 0.285D 03 T TT2.45452
10.000 0.645D 03 Z.80958 0.2740 03 2.43710
11.000 0.324D 03 Z.51099 0.262D0 03 2.4182%
12.000 0.155D 03 2.19012 0.2500 03 2.39789
13.000 0.71CD 02 1.85108 0.238D 03 2.37602
14.000 0.3190 02 1.50382 0.225D 03 2+35259
15.000 0.148D 02 1.16972 0.213D 03 2.32756
16.000 0.767D 01 0.88455 0.2000 03 2.30090
17.000 0.48C0 01 0.68167 0. 187D 03 221257
18.G00 0.363C 01 C.56046 0.175D0 03 2024254

Nt
Table A.5 Output of Program FPTSOILS

TIM=z ANG SPATTIAL UISTRIRUTION JF FISSICN PRAODYCTS IN SOILS

 

-— e e g e, S — - e TRy e i e e e e e ——— v st e - —— — S—— -

ACFULL TANK

 

CONTACT FALCTOR = 7,9 000
T",’;[TT’TV T L AR L Y T T T S T T T S ST s s e
GPOUNCWATER VelnCITY = .7CC4ETCD\ P”P DAy
WQ"S"Q - : \(-CTT’T TS T e e et e e e i e S e e 7 5 re oy st g 24 < s
”D‘UVJW TER "fuCC“TQfTIQ” = Ca22CC
THF = ; T I { L 2 L FYE H F TtH—T =TT ':_;77‘7‘ T T T T T T e e T e e CTTTT T T T T e e e rm e e e e
O ISTENCE TO SUEFLCE w”TE" = -?.JLMMET FQ

 

 

 

 

 

 

i P — — - e S — ———— s = - - — - - e e - pm— - - — - S o

ACTIVITY DUE T SR &C

CISTRIBUTION COSFFICIENT EF TREAKTING “T‘_—UTI =TT DYy T T T e e e oo e e s e e

WISTKIHUTIJVCXFPFTr{r“T FOR GDIUMPWFT = 5?.05(@

m: L I‘fif""’ [ 7 5,7 ( xYF X § e e e S e e+ e s i i+ S e e s e e e e e e
INITIAL ACTIVITY IN LEAKIMG SJLUTICM = fi.? E“O“an nE

SALT CCMCENTRATION F°ACTIDN LOST

 

 

ACTIVITY LrVEL LDG fiFTIVITY L VEL

 

 

e 2127T30-01 =-1.679 r,Ninss 0 54450-07

h N Ls U T T T T e Ty TR T T T QY RRIT T T e 2 REGD =Y
Gal7R2950 Q4 2,253 Z.0012°2 0e5123D-02
TN R AR AT T aLsenT T ' R,7C27Y T T 0, 28T5D=01

£.122270 OF 4,C37 £, 17404 0.7207D-01
TGN R T e g g R T T TR GISEEY T T 0, TaggD TN
Col9h1LD 05 4e272 6e BCLLS Ne2445D 00
CoYeTN ey T T T T T T LT AL T T T T SR T T T T S XSO
L 185470 0OF Gbe1n2 Be 44276 C.43210 0OC
T TS Y T T T T T T T T T s T T T 3 O0405 T T T T 5000000
Co76D61n & 2.€56 2.61€52 Ce5¢71D 00
T LT B AT LT T T T T T TR T T T T T T T T 1 @ ARENE T T T T T T (3B TRYD 00
C.29%060 (4 2,476 1.0E€79 0.5978D 00
Y T T T T s g T T T T T T T T T T R T T T T g R 9T T T T R BTIC2DT T
G500 Del161en 02 34057 Ce&l122 C.6178D0 00
R I LU T T T RSO O E T T T T T T T T T T R T T T T T T R g 2R AL T T T T T Ty 62250700
I vale Cabz71T0 27 2.F21 Cel1E855 0462540 GO
TN T T T T IRLTST TC3 - ZSETT TS QL0956 T 08 2710 00T
3o B00C P 182240 03 2204 Ce 05399 0.62820 00
7 T

 

 

 

 

 

 

o - Ne AR &I O T T T T T T Ge3TTT T T T TG L0685 T T 0L, b 2890 U0

gt
A.3.

Ak,

145

Appendix A--References

E. Glueckauf, "Theory of Chromatography, Part 9--The 'Theoretical

 

Plate' Concept in Column Separations," Trans. Faraday Soc. o1, 3l -
L (1955).

D. G. Jacobs, "Sorption of Cesium by Conasauga Shale," Health
Physics k4, 157-163 (1960).

D. G. Jacobs, '"Ion Exchange in the Deep-Well Disposal of Radioac-

!

tive Wastes," pp. 43-54 in Proceedings of the International Col-

 

loquium on Retention and Migration of Radioactive Ions in Soils,
Saclay, France, October 16-18, 1962.

B. F. Hajek, Plutonium and Americium Mobility in Soils, BNWL-CC-925
(Nov. 28, 1966).
‘“

147

ORNL-4T62
UC-T0 — Waste Disposal and Processing

INTERNAL DISTRIBUTION

1. Biology Library 86. F. M. Empson
2-li. Central Research Library 87. E. J. Frederick
5. ORNL - Y-12 Technical Library 88. D. E. Ferguson
Document Reference Section 89-118. TFerruccio Gera
6-56. Laboratory Records Department 119. J. H. Gibbons
57. Laboratory Records, ORNL R.C. 120. J. H. Gillette
58. ORNL Patent Office 121. H. W. Godbee
59. E. D. Arnold 122. R. F. Hibbs
60. J. A. Auxier 123-142. D. G. Jacobs
61. S. E. Beall 143. W. H. Jordan
62. Myer Bender 14k, J. L. Liverman
63. D. S. Billington 145. T. F. Lomenick
64. R. E. Blanco 146. W. C. McClain
65. J. 0. Blomeke 147. K. Z. Morgan
66. A. L. Boch 148. D. J. Nelson
67. W. J. Boegly, Jr. 149. J. P. Nichols
68. C. J. Borkowski 150. A. H. Snell
69. B. F. Bottenfield 151. W. S. Snyder
70. G. E. Boyd 152-156. E. G. Struxness
71l. F. N. Browder 157. D. A. Sundberg
72. K. B. Brown 158. Tsuneo Tamura
75. F. R. Bruce 159. D. B. Trauger
74. T. H. J. Burnett 160. A. M. Weinberg
75-82. K. E. Cowser 161. George Cowper (consultant)
8%3. F. L. Culler, Jr. 162. J. C. Frye (consultant)
8t. Roger Dahlman 163. E. Gerjuoy (consultant)
85. Wallace de Laguna 164. R. C. Thompson (consultant)

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USAEC, RDT Site Office (ORNL)

165. D. F. Cope
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USAEC, Washington, D. C. 20545

167. C. B. Bartlett
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172. W. H. McVey
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174. Frank Pittman
175. A. J. Pressesky
176. R. M. Richardson
177. W. H. Regan
148

USAEC, Washington, D. C. 20545

178. Milton Shaw
179. J. R. Totter

»
180. D. J. Donoghue
181. 0. P. Gormley
‘ 1
USAEC-0RO
182. TLaboratory and University Division
183. Patent Office
184. J. A. Lenhard
185. J. H. Hill
Battelle Pacific Northwest Laboratory, P. 0. Box 999, Richland,
Washington 99%52
186. R. E. Brown
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192. D. J. Brown
193. R. E. Tomlinson '
194. J. H. Warren s

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Aiken, South Carolina 29801

195. Henry J. Horton, Jr.
196. C. M. Patterson

AEC-IDO, P. O. Box 2108, Idaho Falls, Idaho 83401
197. K. K. Kennedy

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198. J. A. Buckham
199, G. E. Lohse

200. Cyrus Klingsberg, NAS-NRC, 2101 Constitution Avenue, Washington,
D. C. 20418

20l. J. H. Rust, Department of Pharmacology, University of Chicago,
o947 E. 58th Street, Chicago, Illinois 60637

202. F. L. Parker, Vanderbilt University, Nashville, Tennessee 37203

205. George D. DeBuchananne, Chief, Office of Radiohydrology, Water
Resources Division, USGS, Washington, D. C. 20242 1

204, M. King Hubbert, USGS, Washington, D. C.
4

205.
206.
207.
208.
209.
210.
211.

212.

213.

21k.

215.

216.
217.

218.
219.

220.
221.

202,
003,

22k,

225.

226.
227.
228-237.
238.
239.

149

W. W. Hambleton, Director, the State Geological Survey, Uni-
versity of Kansas, Lawrence, Kansas 6604k

C. Fairhurst, School of Mineral and Metallurgical Engineering,
University of Minnesota, Minneapolis, Minnesota 55455

E. J. Tuthill, Brookhaven National Laboratory, Upton, Long
Island, New York 11973

J. A. Lieberman, Environmental Protection Agency, Washington,
D. C.

John E. Galley, P. 0. Box 1346, Kerrville, Texas 78028
Leonard E. Obert, Chief, Applied Physics Research Laboratory,
U. S. Bureau of Mines, College Park Research Center, College
Park, Maryland

C. V. Theis, U. S. Geological Survey, P. 0. Box 4369, Albuquer-
que, New Mexico 87106

E. F. Gloyna, University of Texas at Austin, Department of Civil
Engineering, Environmental Health Engineering, Engineering Lab-
oratories Building 305, Austin, Texas 78712

J. A. Swartout, Union Carbide Corporation, 270 Park Avenue,

New York, New York 10017

Don L. Warner, Cincinnati Water Research Laboratory, Federal
Water Pollution Control Administration, Department of Interior,
Cincinnati, Ohio 45202

Thomas P. McCann, Staff Geologist, Shell Canadian Exploration
Company, Houston, Texas 77025

George S. Garbarini, Sun Oil Company, Denver, Colorado 80201
Louis I. Briggs, Jr., The University of Michigan, Ann Arbor,
Michigan 48104

R. W. Edmund, Augustana College, Rock Island, Illinois 61201
James A. Peterson, University of Montana, Missoula, Montana
59801

A. F. Van Everdingen, Vice President, DeGolyer and MacNaughton,
Dallas, Texas 75206

Frederick L. Stead, Consulting Geologist, Magnolia, Arkansas
L7155

R. H. Burns, AERE, Harwell, Didcot, Berkshire, England

H. Krause, Gesellschaft fur Kernforschung M.B.H., Karlsruhe,
Germany

H. Borchert, Institut fur Tieflagerung, Bornhardtstr. 22, 3392
Clausthal-Zellerfeld, Germany

Klaus Kthn, Gesellschaft fur Strahlenforschung M.B.H., Institut
fur Tieflagerung, Bornhardtstr. 22, 3392 Clausthal-Zellerfeld,
Germany

R. Rzekiecki d'Alergron, S.E.S.R., Center d'Etudes Nucleaires
de Cadarache, P. 0. Box No. 1, St. Paul les Durance 13, France
Bruno Accordi, Istituto di Geologia, Universitd di Roma, Rome,
Ttaly

Carlo Polvani, Divisione Protezione Sanitaria e Controlli, CNEN,
Viale Regina Margherita 125 - 00198 Rome, Italy

Enzo Tansiti, Divisione Sicurezza e Controlli, CNEN, Viale
Regina Margherita 125 - 00198 Rome, Italy

Fabio Pantanetti, CNEN, Viale Regina Margherita 125 - 00198
Rome, Italy
2L0.
2k 1.

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259.
260.
261.
262.
263.
26k .
265.
266.

267.
268.

269,

150

Osvaldo Tlari, Divisione Protezione Sanitaria e Controlli,
CNEN, Viale Regina Margherita 125 - 00198 Rome, Italy .
Guido Branca, CNEN, Centro Studi Nucleari Casaccia, Casella

Postale 2400, Rome, Italy >
Mario Mittempergher, CNEN, Centro Studi Nucleari Casaccia,

Casella Postale 2400, Rome, Italy v
Giorgio Magri, CNEN, Via Generale Bellomo 83, Bari, Italy .
Giorgio Nebbia, Istituto di Merceologia, Universita di Bari,

Italy

Maurizio Zifferero, CNEN, Viale Regina Margherita 125 - 00198

Rome, Italy

Giacomo Calleri, CNEN, Viale Regina Margherita 125 - 00198

Rome, Italy

Carlo Salvetti, CNEN, Viale Regina Margherita 125 - 00198 Rome,

Italy

M.Y. Sousselier, Commissariat a 1l'Energie Atomique, Chatillon -

sous - Bagneux, France

E. Wallauschek, OECD-ENEA, 2 rue Andr€ Pascal, Parls 16e, France

I1.G.K. W1lllams, OECD-ENEA 2 rue André Pascal Paris 16e,

France

Vincenzo Cotecchia, Facoltd di Ingegneria, Universitd di Bari,

Italy

J. P. Olivier, OECD-ENEA, 2 rue André Pascal, Paris 1l6e, France

Felice Ippolito, Istituto di Geologia, Universitd d4i Napoli,

Italy s
Roberto Colacicchi, Istituto di Geologia, Universitd di Perugia,

Italy

Giovanni Merla, Istituto di Geologia, Universita di Firenze, 4

Italy

Raimondo Selli, Istituto di Geologia, Universita di Bologna,
Italy

Paoclo Berbenni, FAST, P.le Rodolfo Morandi 2, Milano, Italy
ISVET, Attention of Professor Adami, via Nizza 154, Rome, Italy
Pietro Giuliani, Divisione di Sicurezza e Controlli, C.N.E.N.,
Viale Regina Margherita 125 - 00198 Rome, Italy

Oscar Ravera, C.C.R. EURATOM, Ispra (Varese), Italy

Argeo Benco, C.C.R. EURATOM, Ispra (Varese), Italy

E. D. Goebel, Kansas State Geologlcal survey, Lawrence,

Kansas 66044

J. E. Wilson, Consolidated Gas Supply Corporation, Clarksburg,
West Virginia 26302

K. T. Thomas, Bhabha Atomic Energy Establishment, Apollo Pier
Road, Bombay 1, India

E. E. Angino, Kansas State Geological Survey, University of
Kansas, Lawrence, Kansas 6604k

André Barbreau, C.E.A., Centre d'Etudes Nucleaires de Fontenay
aux Roses, Fontenay aux Roses (Seine), France

L. H. Baetsle, BELCHIM, Mol-Donk le 200 Boeretang, Belgium
Giuseppe Lenzi, C.N.E. N., Centro Studl Nucleari Casaccia,
Casella Postale 2400, Rome, Italy ¥
Giuseppe Cassano, C.N.E.N., C.R.N. Trisaia, Policoro (Matera),

ITtaly
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270.
271,
272,
273.
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275.
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151

Giuseppe Orsenigo, C.N.E.N., C.R.N. Trisaia, Policoro (Matera),
Italy

R. L. Nace, Water Resources Division, U. S. Geological Survey,
Washington, D. C. 20242

J. C. Maxwell, Department of Geological Engineering, Princeton
University, Princeton, New Jersey

Otto Kopp, Department of Geology, University of Tennessee,
Knoxville, Tennessee 37916

Geological Society of America, Attention of Executive Secretary,
P. 0. Box 1719, Boulder, Colorado 80302

American Association of Petroleum Geologists, Attention of
Executive Secretary, P. O. Box 979, Tulsa, Oklahoma 74101l
American Petroleum Institute, Attention of Executive Secretary,
Corrigan Tower Building, 212 N Street, Dallas, Texas 75201
Given distribution as shown in TID-4500 under Waste Disposal
and Processing Category (25 copies--NTIS)
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