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ORNL-2464.txt
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AL LARORATORY LIBRARY ’;‘//‘__.—.;\
I i
!I_‘I\_ill.ll_!!&h[“|_I|llilmh_";'_\.“h\.lihll.-.i|:\..lu.|l\_| CENTRAL RESEARCH LIBRARY
193 & DOCUMENT COLLECTION
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3 4y5
ORNL-2464
UC-80 Reactors-General
TID-4500 (15th ed.)
ART REMOVAL AND DISASSEMBLY
A. A. Abbatiello
F. R. McQuilkin
OAK RIDGE NATIONAL LABORATORY
operated by
UNION CARBIDE CORPORATION
for the
U.S5. ATOMIC ENERGY COMMISSION
Printed in USA, Price & Availeble from the
Dffice of Technical Services
Department of Commarce
Washington 25, D.C.
LEGAL NOTICE
This roport was prepared as on occount of Government sponsored work. Neither the United States,
not the Commiszion, nor any persen ccting on behalf of the Commission:
A. Mekes wmny werronty or representation, expressed or implied, with respect to the sccuracy,
cemplatensss, or usefulness of the informotion contained in this report, or that the use of
any Information, epparatus, method, or process disclosed in this report moy not infringe
privately ewned rightz; ar
B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any informotion, appaoratus, methad, or process disclosed in this 'rnpefl.
As used in the obova, ""person ccting on behalf of the Commission' includes aony employee or
confractor of the Commission, or employse of such contracter, to the extent that such employee
or contractor of the Commission, or employee of such contractor prepares, disseminates, or
provides access 1s, any information pursudnt-to his employment or controct with the Commission,
or his employment with such contractar. i
Contract No, W-7405-eng-26
REACTOR PROJECTS DIVISION
ART REMOVAL AND DISASSEMBLY
A. A. Abbatiello and F. R. McQuilkin
DATE ISSUED
MAR 4 1960
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION
ORNL-2464
R
mm o 0N W
CONTENTS
e INTRODUCGTION .ottt st cas s et st st e sb s s st s s e b a s s on e s basa s basbensessssatsasases
OBJECTIVES AND CRITERIA oottt crtseiste s ceststssava st et ssessas et e sonssresessessssassssssesessnsssssessss
FRfOrmation REQUITEd.. ..o ettt r et et e s e e e e b e s sbesenas etentessnasasseesesseensarons
Problems Considered ...ttt et e ettt et aete s bt s eaearer et e bt tereeret e enen b bees
Off2Gas LeaKage . coocuiiieeiiiiieiitie ettt st sttt e sttt ats s eas se e teasasbesaasaens sesesaasternsntesnssesseestssnseseress
ReEMOVAI MEthods ..ocueeiieee ettt et s et et e s m e e e s s essese e tessersens satesensasesasnnas
Disassembly Facility .o et st ns e e st saa b s bans s et eaans
REMOV AL oottt ettt eere et vee e teae s e e s tat e e seesas s e e e e sanaee sesssnea e sesassaseasasnssss seantsnsssassassnsasassorsnssssrnnnsns
Philosophy and General Plan for Removal ......ccooveiiiinininceiiececnnin et csresses s esnssssssssssssnens
RAIOGCHIVITY ittt et ettt b sate s bs e e e bt esbeeseesabeeaeaesssessaeabasabesabessaesneeensennsaenesantenstesnsaensas
Access into the 7503 Cell .. e ettt e e et a st s e s e s e et a e s e e e ennennas
Severing the Reactor for REMoval ..ottt sttt et ere s b eaaateeae
W NArawal OF the Re GO Or woooveiieeecciie i e eeeeteeseeeeteteeesases e asesaassasesaeeaeasansasesssssasnsesssssssusssssansnnnsussaseeesssnsas
DISASSEMBLY ..ottt ittt et et e et et be bbb a e s ee bt ebabesttats b ebe st emeab b et abebesbeseas shesenbere e eteasebebeseaseabarane
Disassembly in the Hot Cell ..ottt sr e et s et bs s beas b b erebas s et s bessans
Hot Cell EQUIpMent Criteria oot ettt es s etsaei bt et ass s st s e s bseseben b esemeaeensebsetersessssa s
CUtING MEhod S oottt ettt e et e e e b se e e besbesaeeaesabetesssbaansen
Methods of MeasSUIEMENT .. ...cieeeieerteieeee ettt tete et et et et ere e he et e ae e e et s esns serseemteaantesaas e eaes seeseebeeas
SPECIAL STUDIES oiioteiiiietetetteeteissee e seesetes s ete st ssasseses bbb ssansanessesasesbusssssessestasnsesessesentsasesesssessensesnsns
ShiElding StUIES eeveei ittt e et e st e seas e e s et s nt e sn e en e et g st e s e s s e neeenes
Decontamination of Pressure Vessel, Hot Cell, and Tools ...coovooeieiniinieien e
Size Distribution of Waste Particles from Severance Techniques .....ccoooeiverivimiiniicnncni i
Disposal of Radioactive Materials ....c.coevieirnenriceiini ettt ne s sae s
Facility Mockup for Cold Testing... oo iriconieceioniite ettt s e
Underwater Disassembly STUAY .o et s s seares et ses seeseaseseseaens crasaesensseses
F A G L T Y et et ees et st e b e s e s e en e e sa e s et £ e anae e e aeneeeeare e s renae st sae e b
Consideration of 7503 Facility vttt e s s
Consideration of Other Arrangements.........ccvevirriieneeiiien ittt bbb
Proposed Facility oo e e e
St INVESH GATIONS 1ouieiiiiiiieriseeesse sttt ettt e sene seme et sae bt s st b ae st s aes e sr e a bbb bbb ea bbb nes
Scale Model of Large Hot Cell .ottt e e
. SCHEDULE AND COST ESTIMATE .....ccccvves et eeeeee e et e et et eeehae e e e e ah e e e tee et eaas e e b as et s b sne e s resenneaan
SR AULE e et e e e e e e eae e e aaeeetan——————meennaesee b eetoetnneetesutestatnesstutentrasreraatsaastrntasaeraarnras
OSt E S imM@t® ovovvveeieirerererssuseeessenereaessesanaeseseaneaeenressbesaassesaesssssssusssssssatasnssessanssnsssasssssssnensnssssrassntssnsessrararsnsons
ACKNOWLEDGMENTS -ttt sttt sttt st e sh bbb e st sh e ber e s e snsans e e snes
APPENDICES
COMPILATION OF REQUIRED ART SAMPLES, MEASUREMENTS, AND
EXAMINATIONS .ottt sttt s ae s b s be e va s b e bR b sh e ek s s b ek e e s be st e s e banaeba e sara s
. OUTLINE OF ART DISASSEMBLY PROBLEMS ..ot
RDHC HOT CELL EQUIPMENT oottt ittt sa e s sas e s e sas s be s sasi e s
. ABRASIVE GRINDING INVESTIGATIONS .coiiiciiiericititinins ettt b s sre s s
HELIARC TORCH CUTTING oottt sns s s as s eas sasens s e sab s et
ULTRASONIC CUTTING (ALSO CALLED MAGNETOSTRICTION)....coomiiiiitiniit e
G, ELOX CUTTING . ettt sttt st sr e bbb bbb ettt e b e s b e s bbb bt s b assaesbeaneb b see s 76
H. A COMPARATIVE CONTOUR MEASURING SYSTEM...cciiviiiiimirice ettt s 78
. FLAME SPRAYED REPLICAS. ..ottt sttt ssebe sttt st st s s s s b b 80
J. SPRAYING OF GYPSUM CEMENT .ottt s eriinssss et snes e s s 81
K. CAST GYPSUM CEMENT REPLICAS ..ot s 82
L. OPTICAL MEASUREMENTS THROUGH HOT CELL WINDOWS (ZINC BROMIDE)...ccoccvevemeueieierine. 84
M. OPTICAL MEASUREMENTS THROUGH HOT CELL WINDOWS
(EARLY DESIGN LEAD GLASS) ittt sttt svsn et s e sassarrbsn s sb et a e 86
N. OPTICAL MEASUREMENTS THROUGH HOT CELL WINDOWS
(CURRENT DESIGN LEAD GLASS) oottt st sresaeas sasissnsnsssansnsestevsess s s se s 88
0. ART DISASSEMBLY CELL (ADC) FACILITY CRITERIA .o s, 91
P. SITE INVESTIGATIONS — REACTOR ENGINEERING HOT CELL
A L T IES ettt e s et ee e e et e s et sae e s e st e nebecnebesat sete sarateenen 116
ABSTRACT
A study of a high-level-activity hot cell for the major dissection of the ART was made. Such
dissection was necessary to obtain metallurgical and design data on which future high-performance
reactors might be based, The study included severing ond removing the reactor from the test cell
after operation, o procedure for a component removeal sequence, and a proposed disessembly build-
ing facility.
Evaluations of handling, measuring, and cutting techniques for remote work are presented. Al-
though these are based on limited experimenta!l work, progress is edequate to indicate their poten-
tial value for any high-level reactors which must be hondled ofter irradiation. In many cases details
of the work in the form of the original report have been included in the Appendix.
With the termination of the ART project in September 1957, the draft for what was to have been
a status report was revised to become this termination report. Thus, the plans ond experimental
work are recorded for those who may find the information useful on similar problems.
ART REMOVAL AND DISASSEMBLY
1. INTRODUCTION
The major effort of the ANP program at ORNL was
directed toward the construction and operation of a
reactor known as the Aircraft Reactor Test (ART).
It was expected that much information would be de-
rived during the scheduled 1000-hr test period.
However, there were many items which could not be
learned except by disassembly and careful analysis
of the reactor itself after the completion of the oper-
ating period. With the recent decision not to com-
plete and operate the reactor, actual performance
and test data will not be available, but the detailed
planning carried out for the disassembly of this re-
actor should provide a sound basis for any com-
parable reactor.
Because of the unusual performance requirements,
the ART was to operate with power densities many
times higher than had heretofore been obtained.
Weight limitations for aircraft reactors require a
highly refined design in which many of the parts
may undergo plastic deformation during operation.
While predictions of the conditions of the ART re-
actor parts have been made, based upon careful
analysis of a long series of experiments on a
smaller scale, it is not possible to duplicate all of
the operating conditions simultaneously prior to
running the reactor. Thus it was extremely im-
portant that a fairly complete disassembly and post-
mortem examination be conducted on the reactor to
determine how well it withstood the test conditions.
Therefore, the disassembly, inspection, and precise
measurement of the parts, coupled with complete
metallographic examinations, were to be a vital
phase of the over-all experiment.
It was recognized from the inception of the ART
project that disassembly of the reactor would be re-
quired. However, it had been believed that the ART
reactor pit and the hot fuel dump tank pit, plus the
surrounding area in Building 7503, would be ade-
quate and available for the ART reactor as it was
for the ARE disassembly.] Accordingly, this phase
of the project work was not pursued immediately, as
an all-out effort was needed to get the ART reactor
components into the production stage and to modify
and prepare the 7503 building so that it would be
1. E. Crabtree, Disassembly of the Aircraft Reactor
Experiment, ORNL CF-57-3-56 (Apr. 5, 1957).
suitable for the ART test. Sufficient progress was
made in both of these phases to show clearly that
disassembly of the ART reactor would have been a
very difficult operation and that the existing ARE
pits in Building 7503 were grossly inadequate.
In extrapolating experience gained in the disas-
sembly of the ARE, the differences in proposed
power level and operating time for the ART were
taken into account. The ARE was operated for a
total of 100 Mwhr, whereas the ART was scheduled
to operate for a total of 30,000 Mwhr. This increase
by a factor of 300 in the total irradiation of the re-
actor components meant vastly increased difficulty
in disassembly. Since the bulk of the radioactivity
100 days or more after shutdown would be from long-
fived isotopes, the radioactivity would be directly
proportional to the number of megawatt-hours that
the reactor was operated. Whereas disassembly of
the ARE was possible in the Building 7503 pits by
using improvised methods and ‘‘long-handled tools"”’
from above with roof plugs removed (see Fig. 1), the
operation was marginal and certainly could not have
been repeated for disassembly of a reactor having a
radiation level 300 times greater. Both the shield-
ing and dusting problems would have made it pro-
hibitive.
The ARE reactor was a relatively simple piece of
equipment, consisting of six sets of parallel-flow
pipe runs, each formed into a serpentine shape with
a series of U-bends arranged with headers at either
end, surrounded by the solid moderator and all con-
tained within a welded tank. Disassembly of this
unit was accomplished by removing the end plates
and pipe header manifolds, cutting the U-bends from
one end, and pulling all remaining pipe from the re-
actor container. However, the ART reactor (Fig. 2)
is a complex piece of machinery which is best de-
scribed as a multilayer pressure vessel because of
its multiplicity of precision-made shells, or casings,
which either direct the flow of the fuel or encase
such components as the reflector-moderator, the
boron carbide shield, and the several sodium pas-
sages required for internal cooling. Atop the reactor
is the north head, consisting of a series of pre-
cision-built labyrinth-type channels. Heat ex-
changers built to close-tolerance specifications
were to be located within the fuel-channel layers of
the vessel and within the north head. Because of
the numerous precision-built parts in this reactor, it
UNCLASSIFIED
PHOTO 14205
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el
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Fig. 1. Disassembly of the ARE. Main fuel pump being lifted from cell.
UNCLASSIFIED
ORNL-LR-DWG 16041
FUEL PUMP
CONTROL ROD .
.
.
Na EXPANSION TANK .
NoK
FUEL EXPANSION TANK.._
Na-TO-NoK
HEAT EXCHANGER - _
=
LJ
: z
3 HEAT EXCHANGER
2 ASSEMBLY
- —~PRESSURE
SO SHELL
REFLECTOR 7> N
ASSEMBLY . _ J|FUEL TURN
T VANES
~, N
.,
~,
DN
THERMOCOUPLE
JINSTALLATION -
v NN \‘\\\k
S
SRR
TILE LAYER -~ |}
~
~
S
~ BERYLLIUM ™/
- REFLECTOR— /"~
“ MODERATOR .|~
A
e
~FUEL-TO-NoK
HEAT EXCHANGER
SPHERICAL B,C
TILE LAYER
. THERMOCOUPLE SLEEVE -~
FILLER PLATES
FUEL DRAIN-—
Fig. 2. Cross Section of the ART Reactor.
was known that both the assembly process and the
disassembly operation would be difficult and te-
dious.
Since the ARE reactor was essentially a plumbing
system, the principal types of information sought by
disassembly were those obtainable from chemical
and metallurgical studies. Since the unit was rela-
tively simple and operated at very low stress levels,
there was no need for accurate physical measure-
ments to determine dimensional changes resulting
from its operation. However, the ART reactor is de-
signed very closely; in fact many parts were ex-
pected to deform no more than 0.2% during the start-
up and off-design-point operations. Many non-
nuclear tests, such as the ETU, were planned to
prove the design insofar as possible, but without
nuclear heat the actual temperature distribution can-
not be exactly duplicated. Therefore precise
physical measurements were to be taken after oper-
ation to confirm many of the decisions made during
the design, assembly, and operation of the machine.
For these reasons, the requirements for postoper-
ation measurements and samples for chemical and
metallurgical studies were numerous.
Accordingly, approximately a year ago a concerted
effort by the ANP Project was started to examine
the problems of ART reactor removal and disas-
sembly. Although the experience gained from the
ARE disassembly was available, the fact remains
that neither the Oak Ridge National Laboratory nor
any other USAEC installation has performed a
thorough dissection of a radioactive reactor to
obtain information such as that required for the
ART.
Therefore the objective of developing a program
for safe removal and disassembly of the ART con-
stituted something of a pioneering effort in a new
field. Significant progress was made; however,
much of the work is preliminary. Even so, it was
deemed advisable to bring together in one report the
results of work accomplished. This is a termination
report designed to present the plans, methods, and
information as tentatively developed.
Not only has preparation of the report provided the
authors another opportunity to evaluate the numerous
facets of the program, but its study by reviewers
should stimulate development of program improve-
ments and application of this information to other
reactor studies. The authors, therefore, solicit com-
ments and suggestions from readers. -
In general, the investigations have been divided
into the following categories:
1. Removal: disengagement, withdrawal, and
transportation of the radioactive reactor and com-
ponents from the Building 7503 operations cell to
the disassembly hot cell
2. Disassembly: dismantling of the radioactive
reactor and components in a hot cell plus obtaining
the required postoperation specimens and infor-
mation
3. Special studies: shielding studies, particle
size distribution, cutting methods evaluations,
sealing systems, replication and measuring tech-
niques, and scale models
4. Hot cell facility: the physical plant, including
dismantling hot cell, service and maintenance hot
cell, hot storage, and basic equipment as required
for the disassembly operations -
Before the detailed discussions under the above
headings, a discussion of criteria has been included
to make the program objectives more definitive. For
completeness, a brief review of tentative schedules
and budget considerations is presented at the end of
the report. A considerable portion of the material
has been included in the Appendix in order to permit
presentation of the information in detail without dis-
turbing the continuity of the report.
While the development of handling methods, meas-
urement techniques, and cutting processes has been
directed toward a specific reactor, namely, the ART,
it is believed that many of the features are appli-
cable to the dismantling of other large reactors.
Certainly the basic schemes may be adapted to
other disassembly situations. Experience has in-
dicated that each new advance in technology re-
quires a corresponding advance in its associated
facilities. Thus, the highly radioactive reactor
equipment requires specialized methods capable of
safely handling the physical units. The necessity .
for working through remote devices increases the
difficulties by a large factor. |t is realized that
practically all new reactors will be faced with
similar problems, and any solutions which are de-
veloped during this work should find application in
reactors which follow.
2. OBJECTIYES AND CRITERIA
Information Required
The major types of information required from dis-
assembly of the ART were:
1. information and dimensional data on the effects
that power operation of the reactor has upon the
structural stability, distortion, warping, crack-
ing, and local behavior in the vicinity of welds,
brazed joints, ete., of all major reactor compo-
nents;
2. chemical analyses of samples of the reactor
parts to determine whether significant reactions
occurred during operation;
3. metallurgical study of specimens from each
region and each major part of the reactor to as-
certain the extent of plating-out of fission
products, if any occurred, and to determine what
changes were brought about by the unique oper-
ation of radiation, temperature, fuel circulating
velocities, pressure, and corrosion;
4. material studies to ascertain the compatibility
of beryllium and Inconel, the integrity of a boron
carbide shield layer and its cladding, and the
effects of radiation damage on various metals,
particularly those associated with the boron
carbide layer;
3. in the event of a failure of any part during oper-
ation, study of the exact conditions at the point
of failure.
The first step after the formation of the ART Dis-
assembly Group was to establish in precise termi-
nology exactly what was required from the disas-
sembly that would satisfy the above general require-
ments.? A compilation of the resulting details can
be seen in Appendix A. A study of the ‘‘before’’
and “‘after’’ measurements required for creep defor-
mation revealed that simpler methods of getting this
data could be devised, as will be explained later.
Problems Considered
Accordingly, steps were taken to identify all
problems and circumstances which would exist or
might arise that would have a definite bearing on
the disassembly operations. Therefore, in an effort
to establish an early set of design criteria, a report
entitled Outline of ART Disassembly Problems was
prepared and discussed with all parties who were to
2L. W. Love, Meeting on Measurements Related to ART
Disassembly, ORNL CF-57-4-31 (Apr. 12, 1957).
be concerned with this project. This report is pre-
sented herein as Appendix B.
At this stage it was recognized that the ART Dis-
assembly Group could progress faster if the group
could review its work and problems frequently with
Project management as well as others concerned.
Accordingly, a “‘Disassembly Planning Meeting'’
was organized on a semiformal basis. In the weekly
meetings during late 1956, considerable assistance
was obtained through the establishment of several
important criteria, particularly those dealing with
the conditions for which shielding, ventilation, and
accessibility are vital. Minutes of these meetings
are available in the Project records; however, all
technical data have been included in this report in
the appropriate places.
Another major step in the establishment of criteria
was a series of studies of the postpower operations
and shutdown procedures for the ART. From these,
determinations were made of likely starting con-
ditions for removal and disassembly of each com-
ponent. A. P. Fraas® prepared the first report on a
general basis at the outset of the disassembly pro-
gram; W. B. Cottrell4 reviewed the problems in
detail late in 1956.
Off.Gas Leakage
In connection with shielding requirements, a de-
cision was made to establish an arbitrary, though
realistic, radiation source of a certain intensity that
could be used for calculations. Accordingly, an as-
sumption was made that during the operation of the
ART there would occur from the reactor inside the
pressure vessel an ‘‘off-gas’’ leakage of 1%. This
value is considered to be an abnormal one with ref-
erence to a successful and normal operation by the
ART, but it is believed that the use of this figure is
conservative and also provides a safety factor ex-
cept in the case of a major reactor failure. Activity
levels have been calculated for normal reactor oper-
ations and have been reported.®
Removal Methods
The exact method of removing the ART from the
pressure vessel was not determined; however, five
3A. P. Fraas, Disassembly of the ART, ART Design
%V\emc)) No. 2-A-1, ORNL CF-DM-55-1-104, vol 1 (Aug. 8,
956 .
4w. B. Cottrell, ART Disassembly Operating Proce-
dures, ORNL CF-56-12-131 (Dec. 27, 1956).
SA. P. Fraas and A. W, Savolainen, Design Report on
the Aircraft Reactor Test, ORNL-2095 (Dec. 7, 1956).
methods or basic types of equipment were analyzed.
The final selection of one of these methods would
have established most of the design criteria asso-
ciated with the ART removal phase of this program.
The five principal methods considered were:
1. radisphere,
flat top or floating floor,
remote C-crane,
rigid polar,
. swinging polar.
S SEANN
Studies indicated that either the floating floor or
the remote C-crane was likely to be the most
practical method, with the final selection to be made
on the basis of existing activity level, accessi-
bility, and cost.
Disassembly Facility
With regard to the large hot cell facility, design
criteria were established in rough draft form as pro-
posed for submittal to an architect-engineer. The
architect-engineer, in turn, was to prepare the de-
tailed engineering and construction drawings for the
facility. In addition to the problems associated with
space, equipment, maintenance, and basic design of
the large hot cell, two problems that were of par-
ticular concern were contamination and personne!
shielding. The air-borne radicactivity would require
adequate filtering systems and a negative air pres-
sure within the cell in order to keep the operating
area low in activity. Complete circulating, filtering,
and disposal systems were required for all working
solutions, such as cutting fluids, decontaminants,
and wash solutions. Personnel shielding was to be
provided by 4'/2-ft-fhick barytes concrete walls and
shielded viewing windows.
3. REMOVAL
Upon completion of operation of the ART it was
planned? that, while the pressure vessel of the 7503
cell was still closed, all the process fluids would
be transferred to their respective removal containers.
The fuel system was to be rinsed, the NaK was to
be removed, and the sodium was to be drained from
all parts of the reactor except the contro! rod. All
these operations were to be performed by remote
control. After sufficient time for decay of activity
in the fuel, the cell (Fig. 3) was to be unsealed and
cautiously opened. At this stage the program for
disassembly of the ART was to begin.
Philosophy and General Plan for Removal
While successful removal, transport, and disas-
sembly of the ART were to be dependent upon the
radioactivity level of the fuel and equipment, it
must be recognized that the possible activity level
could have been anywhere from very low to very
high. The former represented the case wherein
operational difficulties occurred shortly after nu-
clear operations began, while the latter represented
the extreme case of a near catastrophe, in which
efforts to recover the equipment could yet have been
justified, The normal case was to be that in which
the reactor was successfully operated for 500 hr at
60 Mw without leaks from the off-gas, fuel, NaK, or
sodium systems, and consequently all activity in
the cell would have been successfully contained.
However, for the design case, criteria were assumed
that would represent a situation somewhere between
the normal and subcatastrophe cases. The two
basic situations recognized as causes for trouble- -
some activity were leaks from the off-gas system
and accidents where fuel would get outside the con-
tainers and shields. Either case would require both -
means for controlling or reducing contamination, and
shielding protection for man entry into the cell.
Arbitrarily, it was established that removal design
criteria would not go beyond the case of off-gas
system leaks. Improvised measures would be em-
ployed for worse situations.
To avoid the possibility of contaminated lines at
the manhole and to ensure an early transfer of fuel
to the recovery tank, it was planned to relocate the
control panel for the fuel transfer from the temporary
location on the main floor to the auxiliary equipment
room panel. Also, to eliminate the need for vacuum
distillation of sodium from the reactor, plans were to
permit the sodium in the control rod to freeze. It
was to be removed subsequently from the reactor in
the disassembly hot cell.
To reduce the quantity of sodium within the com-
ponents, the reactor shell sodium and moderator
sodium were to be drained through separate lines to -
a common line having a bismuth valve and then
through the 7503 cell wall to a drain tank in the
radiator pit, It was recognized that residual sodium
would remain in pockets within the reactor.
Because of the possible contamination on all sur-
faces within the cell, it was proposed to wash these
many surfaces down with a portable deluge shower
head. To remove the waste water and to simplify
drainage of the water from shield systems, it was
UNCL ASSIFIED
r S PHOTO 28275
Fig. 3. Model of the ART. The reactor is shown in the operating cell prior to removal.
planned to install a sump pump that could transfer
water to a safe drainage system.
To facilitate removal of components with remote
equipment, it was proposed that every line that had
to be cut should have an accessible horizontal sec-
tion of pipe. The only exception to this was the
fuel drain line. For this, it was first proposed to
preinstall a severance device; however, later it was
planned to use a portable one. Wherever gas leak-
age from severed pipes appeared likely, a sealing
device such as the ‘'sealant injector’’ was to be
used,
In order to reduce spread of contamination in the
building, it was planned to provide a containment
can into which the fuel recovery tank could be
drawn for the transfer. The can was to be equipped
with a blower and filters to promote convection
cooling of the tank.
For removal and transportation of the hot reactor,
it was proposed to drain the reactor water shield,
lift and carry it through the 7503 building with the
remotely controlled 30-ton building crane, and mount
it on a heavy-duty low-boy trailer. If deemed neces-
sary, the reactor water shield would be refilled for
the trip to the disassembly hot cell.
Radioactivity
A compilation of postoperation dose rates as pre-
dicted for the ART is presented in Table 1,
Pursuant to the decision that shielding design
criteria would be based on the off-gas system leak
Table 1. Predicted Dose Rates for ART Reactor*
100 days aofter shutdown
Based on operation for 500 hr at 60 Mw
Dose Rate at
No. Case Shield Surface
(r/ hr)
1 Undrained reactor, 100% of fuel, 6500
no water, and no lead shield
2 2% of fuel, no water shield, and 750
no lead shield
3 2% of fuel, no water shield, but 0.4
with lead shield
4 2% of fuel, water in shield, and 3.5 x 10~3
lead shield
*D. E. Guss, ANP Quar. Prog. Rep. Dec, 31, 1956,
ORNL-2221, p 85; A, A, Abbatiello, Dose Rates for ART
Reactor, ORNL CF-57-7-91 (July 25, 1957).
case, calculations for gamma dose rates and amounts
of beta activity were performed by D, E. Guss of
the Solid State Division, It was assumed that:
1. during the entire operation period 1% of the off-
gas somehow leaked from the off-gas plumbing
system into the 7503 cell,
2, the gaseous fission products which escaped
plated out on the simple geometrical surface of
a 12-ft-radius sphere,
3. the computed dose rate would be based on the
gamma activity of the daughters of these fission
products at 10 days after shutdown following
500 hr of continuous operation at 60 Mw.
For this case the gamma dose rate through a 1-in.
lead shield would be 6 r/hr. The most serious of-
fender in dose would be La'4? with l]/z-Mev gamma-
ray energy. Since it is the decay product of 12.8-
day Ba'40 and has a 40-hr half life itself, the dose
rate should fall fairly fast to the next dose-rate
level as the La'4% decays. This new level is a -
dose rate of 600 mr/hr through a 1-in. lead shield
approximately 40 days following the shutdown.
The amount of beta activity in the cell 10 days -
after shutdown was calculated to be as follows:
Half Life Curies
13 days 710
20 days 1387
28 years 13
Total 2110
Most of these betas are of 1',-Mev energy and have
a maximum range of 18 ft in air. This amount of
activity would require appropriate protection for
personnel in the vicinity of the open manhole. Since
approximately ¥ cm of Lucite should be sufficient
to stop betas at the manhole location, it was recog-
nized that the gamma dose through the cell top fol-
lowing such an off-gas leak might well be the more
serious problem, It would exist immediately upon
lowering of the annulus water level.
Access into the 7503 Cell )
Five methods were considered for providing ac-
cess and for performing the removal from the pres- .
sure cell, These methods are described below and
are compared in detail in Table 2,
1. Radisphere. — This device is a shielded per-
sonnel container with windows and with articulated
cutting tools mounted externally. The operator and
all controls are inside the container, which is at-
tached to the pressure cell crane hook. Precautions
Table 2. Comparison of Pressure Cell Guillotine Handling Systems*
Factor
Relative . o Contamination Failure )
Device Cost Safety Maneuverability Viewing Spread Consequence Advantage Disadvantage
Radisphere 1(10) Bad (0) Fair to bad Good direct; Some (5) Large (0) QOperater can Failure of motors
(55) (10) good TV approach work or controls locks
(30) operator in radia-
tion field
Floating floor 1.25 (8) Good (20) Good (20) Fair direct; Little (8) Small (10) Good air control, Requires maximum
91) good TV visibility, cell opening at an
(25) shielding, and early date
control
Remote C- 0.5 (20) Fair to good Fair to bad Poor direct; Some (5) Small (10) Goed air control Large inertial forces
crane (80) (15) (10) good TV and shielding will make exact
(20) placement difficult
Rigid polar 1 (10) Good (20) Fair to good Poor direct; Some (5) Large (5) Good air control, Long stroke of
(75) (15) good TV shielding, and cylinder (7 ft)
(20) control would complicate
design
Swinging polar 0.75 (13) Good (20) Goed (20) Poor direct; Little (8) Large (5) Good air control, lInertia of tool would
(86)
good TV