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ORNL 528

Copy of 122 Series A.

Contract No. W-7405, eng. 26

THE AIRCRAFT NUCLEAR.PROPULSION-PROCRAM
AND

GENERAL REACTOR TECHNOLOGY

QUARTERLY PROGRESS REPORT

for Period Ending November 30, 1949

A. M. Weinberg, Program Director

Report Edited by
C. B. Ellis

. 7 vaaror oy fORT
DATE ISSUED: 5&.1"\; 16 w,‘-._)

OAK BIDGE NATIONAL LABORATORY

 

This doc{uwent consists of 41 pages.

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MIEOIIEOOTEE g

ORNL 528

Reactors—Progress

o

. Steahly
Mann
Snell
VonderLage
Graham
Larson (Y-12)
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REFWZMOEDODE

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“ : , TABLE OF CONTENTS

~ SUMMARY
INTRODUCTION
REACTOR DESIGN
‘Overall De#ign Studies
"Criticality Theory
SHIELDING
. Design of New Attenuatibn Testing Facilities
Lid Tank Bulk Shielding Méasuréments
Shielding Analysis
Monte Carlo Shielding Calculations |
)Ducted Shield Theory
Pd Film Fast Neutron Detéctor

Neutron Energy Spectrometer

Bl . ae _—

| Shielding Materials_'

Pb-B-H,0 system
Boral

~ Boron plastic

R L L

- >fB6fbn'pfoduction and B'° Sebaratiofi
théretes | - o S
HEAT TRANSFER
Heat Transfer Summary

Heat Transfer in Annuli

r.)}

RER Bl . o

i, ..o

10
10
10
11
11

12‘
13
15

15

15

15

20

20
22
22

23
23

25
25

25
. Polarized Turbulence
Physical Properties of Molten Sodium Hydroxide

i , - The Liquid Metals Program for ANP

METALLURGY AND MATERIALS
RADIATION DAMAGE
Reactor Core Material Studies
Auxiliary Material Studies

Metal hydrides

Plasfics

Sodium hydroxide

Fast flux in Hole 19

High intensity gamma source
¢ | Beta vs gamma dosage |

Lubricants

el L L

)
i

26

26

27

30

32

32
34

34
34
35
37
37
41
41
R kb o el B e s

i LS K T LA BDC e ety e

- LIST OF FIGURES

Fig. 1 'NEPA Proton Recoil Detector Assembly
Fig. 2~ Densities of Pb-B-H,O System
Fig. 3 Neutron Spectrum for Hole 19, ORNL Reactor

- LIST OF TABLES

Table 1 Energy Resolution in the Neutron Recoil Spectrometer

_Table 2 Resistance of Plastics to Irradiation

Table 3 Radiation Stability of NaOH

Table 4"'-Béaétions-USéd td'Défié;hinéfiFést:Flfix

18
21

39

19

36

38

40
oo Ee st Sebltobiekics. o adackche e die

SUMMARY

Reactor Design. Exploratory studies are underway on some possible new
cycles not previously considered for aircraft reactors. New mathematical
methods are also being investigated for ahalysis of reactor cores heving in-
tricate internal geometry.
| Shielding. Possible designs are being studied for a new testing facility
to measure attenuations up to 10°. This should probably be in some form of a
critical assembly which will operate at power levels up to 10 kw.

On the lid tank, bulk shielding measurements of iron and water are now
underway. It is hoped to begin two-shift operation shortly. |

Theoretical analysis is in progress on (a) thick shields composed of a

‘mixture of pure scatterers; (b) neutron penetration of a water shield, using

Monte Carlo techniques, and (c) neutron streaming in ducted geometries.*

A new instrument for measuring fast neutron flux is being developedf This
consists of a thin Pd film fired on a ceramic core. The proton recoils from
the neutrons bombard the Pd in such a wayas to change the electrical resistance
of the film. _ |

The NEPA neutron spectrometer,'based on counting proton recoils from a
radiator, is now installed at ORNL and is being calibrated.”

In the work on shielding materials, combinations of Pb, H,O, and B or B,C
are being studied, and irradiation tests on Boral have been made. The tensile
strength of the latter appears to increase under irradiation. Also, a new
plastic has been developed which contains 50% boron by volume. It may be made

into strong, flexible sheets, mechanically similar to leather, which can be

easily glued‘onto metal surfaces for thermal neutron shielding. Work on im-

proved concretes for shielding also continues.
Heat Transferoj The summary(xfatomlc energy heat transfer work, ORNL 156,

has been broughttq)to date and abrldged for declass1f1cat10n. A new emp1r1ca1

'erelat1on has been developed for heat transfer in annull whlch will hold for

all cases where the l1qu1d wets the walls-—lncludxng 11qu1d metals. It has
been shown that the supposed phenomenon of polarlzed turbulence ‘does not
exist. The thermal conduct1v1ty and heat capac1ty of molten NaOH have been
measured at 900° F. ’

- Equipment is beihg designed for work on handling methods and heat transfer

properties for liquid metals at aircraft reactor temperatures.

® These projects are being conducted in collaboration with .NEPA.
RS R D s i

R R o

AT G v e GRS LARCRE. L a

Metallurgy and Materiaels. A program is being set up for testing the
corrosion and mechanical properties of many metals when exposed to high tem-
perature liquid bismuth or lithium. Molybdenum has the best corrosion re-
sistance to Bi at 1800° F found so far, with Be also good; however, Ni and
stainless steel are attacked. Larger vacuum furnaces su1table for work with
molten Bi and Li are being built. _

Radiation Damage. Five people from NEPA have now been trained in radia-
tion damage techniques at ORNL. The principal tests on reactor core materials
now underway are on Bé2C° Changes during irradiation of such properties as
electrical resistivity, modulus of elasticity, hardness, coefficient of thermal
expansion, and thermal conductivity are being measured with the ORNL reactor.*
Exposures of Be,C to Hanford flux will be made in the near future. Work on
other possible ANP materials will be begun shortly. |

Because of its interest as a possible shield material, TiH, has been tested
for decomposition under a neutron flux of 0.5 x 102, No radiation-induced
decomposition could be observed during 1800 hours exposure at temperatures
from 160° to 340° C

Decomposition of numerous commerical plastics under irradiation was observed
The most resistant was polystyrene. _

As an a&junct to the radiation damage work, the fast flux in Hole 19 of
the ORNL reactor was measured, using a series of threshold detectors. A curve
of the measured spectrum 1is presented. The total flux above 1 Mev was found
to be 0.11 neutrons/(cm?)(sec) (watt).

A high intensity gamma source free of neutrons, is being prepared by
irradiating cylinders of gold in the reactor. From these cylinders it is ex-
pected that gamma fluxes above 10° r/hr can be obtained. '

Irradiation of speclal lubr1cants for p0381b1e aircraft reactor use 1is

belng contlnued in the ORNL reactor.

* Thege p.rO}ects are being conducted ifi collaboration with N.E.PA,
B e th e e L

el

e ke R

INTRODUCTION

The program looking'towardtfluedevelopment of a nuclear propelled aircraft

is now a joint project of three Government agencies—the Department of Defense,

‘the National Advisory Commlttee for Aeronautlcs, and the Atomic Energy Com-

mission. On September 26 1949, the Atomic Energy Commission designated the
Oak Ridge National Laboratory as the agency for carrying on the AEC's share of
the joint technical program. The other two working agencies are the NEPA
Division of Fairchild Engine and Aircraft Corporation (as a contractor of the
Air Force) and the Cleveland laboratory of NACA. The division of effort be-
tween the three laboratories has not yet been defined in detail. However, the
Oak Ridge National Laboratory has been asked in general to 1nvest1gate the
nucleonics aspects of the project.

- To meet this responsibility, the Laboratory is eipanding its present work
in all Divisions on experiments likely to aid the ANP program, and is also
planning the establishment of new projects with high priority. A number of
pieces of work already underWay were initiated at the request of NEPA and so
apply directly to the ANP program. For at least the immediate future, most of
the experimental ANP work of the Oak Ridge National Laboratory is expected to
fall into four categories: |

Shielding

Heat Transfer

Metallurgy and Materials

Radiation Damage

No preferred reactor type, coolant mechanism, or shielding material for

the nuclear airplane has yet been definitely chosen by any agency. Therefore,
the experimental pfogram.most”still Be exploratory in nature. To guide this
work throughout ORNL a small ANP De51gn Group is being formed within the
Technlcal D1v1s1on "This group w1ll carry out reactor calculations and will

survey and compare the pos51ble overall de51gns, ‘and recommend those materials

~and processes most worthy of study by the Laboratory at any time.

A contlnuous and close llalson at all levels will be malntalned wlth NEPA

-and NACA to avoxd unw1se dupllcatlon ‘and to effect mutual progress “Joint

"experlments with shared personnel and facilities are expected to be of in-

creasing importance.. At present tfiuapersonneliu;ORNL cooperating in such work

8
i B i - A b ¢ ATk M i ©

M e e

number 21 from NEPA and 3 from the U. S. Air Force. About 10% of the ORNL re-
actor usage based on the allocation of operating costs, is devoted to ex-
periments directly for NEPA, | '

The following sections describe presefit and planned work bearing on the
Aircraft Nuclear Propulsion Program throughout the Laboratory. Some of this
work originated at NEPA and is being carried out at ORNL now as part of the
integrated ANP effort. Approximately 42 persons are now doing work directly

related to this program;, in addition to work specifically for ANP there is

_containéd:hlthis report some material affecting reactor technology in general.
e EE ke

»

REACTOR DESIGN

OVERALL DESIGN STUDIES

C. B. Ellis*, Technical Division

Some preliminary and exploratory work has been carried out on a few
possible aircraft reactor designs. These have been chiefly of unusual types
not previously surveyed forrthe'purpose, Included are (a) a reactor moderated
and cooled by molten NaOH, (b) reactors using liquid uranium alloys, and (c)
systems containing boiling liquids, either as coolants or as control agents.
None of these studies are yet complete, however it does appear that the active
cdrelfor;nlNaOH aircfaft reactor might be no larger than two feet in diameter.

It is planned to concentrate the design studies on those heat transfer
systems and reactor types which show promise of permitting very high power
densities in the reactor core. Such work may permit a decision as to which
newrchles, if ahy, should be attacked experimentally at ORNL in addition to

| those already under study by NEPA.

CRITICALITY THEORY

Ln.Nelsoh, Mathematics and Cofiputing Panel

The Mathematics and Computing Panel is investigatihg new methods of
analyzing the neutron distributions and criticality conditions for reactor
cores of intriéate geometry. Special attention is being given to systems
having gaps and ducts within the core, of the sort which may be necessary in a
gas-cooled aircraft reactor. ‘Advantage will be taken of high speed computing
machine methods. One approach to be tried is the three dimensional relaxation

technique.

® U. S. Air Force peréonnei.

10
SHIELDING

The shielding program at ORNL is designed to study simultaneously the
feasibility of shielding mobile reactorsF—particulérly nuclear-powered aircraft
or ships—-and the more long-range problena6funderstan§ingthe shielding processes
so that nearly ideal shields canbe designed. The experimental work will center
~ about two bulk shield testing facilities, one already in operatibn, the other
only recently decided upon and hence in the early design stages. The results
of both experimental programs will be analyzed by a theoretical section which
will be responsible for the guidance of the work. Many of the proposed ex-
periments will correspond closely to the proposals of H. A. Bethel, and as re-
commended by him, emphasis will be placed on the neutron attenuation, which

shows little promise of becoming calculable in the near future.

- DESIGN OF NEW ATTENUATION TESTING FACILITIES

W. M. Breazealeand E . P. Blizard, Technical Division

Although the 1id-tank adjacent to the pile is operating satisfactorily
and is yielding the expected data, it has been evident for some time that an-
other bulk shield testing facility with somewhat different characteristics
should be built. Specifically, the new facility should be capable of measuring
attenuations of some 10%® in fast neutrons, should have a variable intensity
source and should permit measurements through various shapes of shields (i.e.,
cylindrical or possibly spherical in addition to flat plates). The present
11d tank is not capable of such a large attenuation range.

Varlous des1gns have been or are being considered. A fission plate ex-
c1ted by thermal neutrons from ‘the pile obviously will not meet the above re-
quzrements. Some type of critical assembly which can be operated at power
levels up to 10 kllowatts should be satisfactory. The three pos§1b111t1es
which we have consxdered are: (a) bu1ld1ng a "water boiler™; (b) modifying the
- MTR Mock-Up, when scheduled tests are finished, to make it into @& bulk shield
téSting faéility,'and (c) assembling a number of fuel elements, similar to
those now in the Mock-Up, into a small reactor. This last seems to be the
quickest and cheapest prpcedure; The assembly would be operated in a pool of

1. o | .
Report on the Status of Shielding Information for the NEPA Project, H. A, Bethe, June 10, 1949.

11
b g

water both for cooling and shielding purpoées, Detail designs are now being
studied with a view toward predicting costs, and time of construction, and a
.specific proposal will be made in the near future. Suggestions similar to the
above have also been made by R. Echols and J. Bair of NEPA.

LID TANK BULK SHIFLDING MEASUREMENTS

Clifford, Flynn, Lewis*, Hullings, Martin; Technical Division

A. Experimental Program. 1In order to expedite fibeproposed bulk shielding
measurements, additional personnel have been assigned to this program., R. H.
Lewisg‘Jr, Physiciét, with the assistance of M. K. Hullings, Jr. Mathematician,
and K. Martin,6 Jr. Mathématician are now respon51ble for all measurements in-
volving foils, and also for operation and malntenance of the counter room,
Building 105. J. D. Flynn, Chemical Engineer, assisted by D. J. Kirby, Tech-
nician, and V. L; DiRito, Technician, are now responsible for operation of the
lid tank and measurements taken in the tank by the various methods other than
foils. |

The first of a series of attenuation measurements of iron and water is
now underway. This is the attenuation of water alone. Measurements along a
line perpendicular to the source, (28 in. diameter—2 X 10° incident flux) and
integral measurements will be made for both neutron and gamma rays through 210
cm of HQOD2 Following this, the attenuation of a shield containing 80% iron
by volume in the form of 7/8 in. iron plates will be measured.

Other attenuation measurements planned for the future will include about
two more iron-water shields to fix the optimum ratio for that combination,
both with and without an iron thermal shield This data will be used to help
specify requ1rements of wolfram for later attenuation test specimens.

After iron and water, 'the other two-component systems of interest will be
measured to wit:

Lead-water
Wolfram-water
Ironfbdron'
Lead-boron

Wolfram-boron

® NEPA personnel.

2 For thermal neutron distribution aiong centerline of tank see ORNL 480 p. 12,

12
e,

o Banaie

All of these are to be measured with and without metal thermal shields. Each
system will take several months to measure even with the tank operating on two
shifts-walthough this time estimate cannot be very accurate without more ex-
perience on the facility.

B. Status of Tank and Equipment. The source plate, consisting of 200

X-10 slugs, has been placed in the tank. In an effort to calibrate the source

'directly,‘three thermocouples were each welded to a slug in the central row

in order to determine the temperature increase in the source plate caused by
the energy released in it from fissions. The voltage from these thermocouples
is being determined with a v1brat1ng reed electrometer, the maximum sens1t1v1ty
of which is 5 mlcrovolts full-scale. Measurements are now being taken.

To increase the range of the gamma measurements a methane-argon gamma
proportional counter has been installed outside the rear face of the tank on a
line perpendicular to the center of the source. It will remain in a fixed
position and surrounded by a four-inch lead shield.

To avoid excessive loss of time due tomaintenance of electronic equipment,
two proportional counter setups, i.e., two A-1 amplifiers, four scalers, and
two A-1-A preamplifiers have been acquired. These are all new or recently re-

modified by the Instrument Department and are now in operation.

SHIELDING ANALYSIS

W. K. Ergen*, F, H,Mu'rray,lS° Podgor*; Technical Division

The first part of the reporting period coincided with the latter part of
the Summer Shielding Session. The following four reports were issued with

a member of the Shieldifig Analysis'group'és'an author or coauthor:

ORNL 424 "Approx1mate Analys1s of Penetrat1on of Neutrons through
" > a Thick Shleld of Non- Hydrogenous Materlal" by F. H.
e e {Murray -
"ORNL 426 "Total Cross Sectlons of nght Elements as Obtained from
7.7 the Un1vers1ty of M1nnesota , by W. K, Ergen

 0RNL 457.7"Program for the ORNL Bulk Shleld Testing Facility"™, by
o E. P. Blizard, C. E. Clifford, W. K. Ergen, G. Young

ORNL 435 "Neutron and Gamma Attenuation through Tungsten Carbide
' and Boron Carbide™, W. K. Ergen, C. E. Clifford

* NEPA personanel.

13
- A great part of the time of the Shielding Analysis group was spent in

assisting in the issuing of Summe Shielding Session reports, after the authors

v had left Oak Ridge. Some time was also dedicated to the design of a new bulk
shield testing facility at the MIR site, |

F. H. Murray is investigating thick shields composed of a mixture of

elements, some of which may be considered pure scatterers. Consideration of

a large number of spherical harmonics representing the neutron flui as function

of angle leads to a mixed set of equations:
(1 - g, )k, - kK, =0,
(1 - g J)K_ = [ k/(2n+1) ] [ nK__, * (nel)K_o, ],nsN

(d2K/dw? ) + (1/w)(dK/dw) + [2 - 2k y(w)]K = 0, = n + ¥ >N
| y(w) =1 . g(w).

The corresponding Boltzmann equation is

.

- , | (1 - k cos O)K = Q/4m UEL:E:[%%;l}gn K P_ (cos 0).

. ' K represents the Fourier transform of the flux, and is répresented by the
series on the right with g_ replaced by unity; g  is defined by the scattering
as function of angle by the various nuclei, and k is an eigen value such that
1/k0} is the relaxation length in mafiy idealized problems, The recurrence
equations do not seriously add to the computer’s work and can be used for
shielding problems for mixtures to which Wick’s methods are not applicable.

Identities useful in the calculation of eigen functions of a Schrodinger
équation have been developed for this system when the cross sections are con-
stant; for the case of variable cross sections a method of perturbation is
being developed. | |

Also a short memoréndum,was i$éued by W. K. Efgen on shielding of small
reactbrs. Thié @émorandum digcu§Sesvthejféct that'for small reactors short
relaxation iength Bécbmes more important fbr minimum shield weight than low
g/cm?. : - L | | |

Samuel Podgor of NEPA has been assigned to the group.
ceElhE b e e o

LG B W el b e MG e

e b R el B B oan

[¢]

MONTE CARLO SHIELDING CALCULATIONS

L. Nelson, Mathematics and Computing Panel

A Monte Carlo computation (described in ORNL 439) of neutron penetration

of a water shield is currently underway. Thls problem was suggested by the

Summer Work Se331on on Shielding and has two purposes: (a) the results will
be of intrinsic value in shielding considerations, and (b) the results will
indicate a more efficient design of subsequent Monte Carlo computations in

solving similar problems in shielding.

DUCTED SHIELD THECRY

D, Whitcombe*, Physics Division

The report "Solution to the Diffusion Equation with Streaming for Three
Basic Geometries', by D. Whitcombe and N. Smith, has been released as ORNL 403,
The report contains‘the solution to the Helmholtz equation V2 ¢ - k2% =
for various two medium geometries where the boundaries are not coincident with
an equi-flux surface. When'this general condition exists there is a net
current parallel as well as perpendicular to the boundary; and this condition
is de51gnated as "streaming™. This report presents many solutions of this

type for three ba51c geometries encountered in practice, which are sufficient

~to obtain an approximate answer to a general problem in this class.

Pd FILM FAST NEUTRON DETECTOR .
B Gosszck* Technzcal Dzvlston
Prellmlnary 1nformat10n has been obtained on resistance varlatlons of a

palladlum film f1red on a ceramic core, due to recoil- proton bombardment In

view of the large magn1tude of resistance changes, it is proposed here that

.thls re51stor mlght be employed to measure the energy absorbed per gram of

tissue as a result of a fast neutron flux, after L. H. Gray. 3 1t seems rather

certain that the effect is produced by hydrogen occluded in the palladium.

* NEPA per soooe 1.

3. R, Gray, Proc, Cambridge Phil. Soc., 40, 72 (1944),

15
e B R S w3

n

The resistors which have been exposed thus far were manufactured by Continental
Carbon, Inc., according toa process described in "Printed Circuit Techniques'™,
National Bureau of Standards Circular #468, November 15, 1947, page 16,
Through the courtesy of Dr. J. W. Jira, of Continental Carbon, resistors with
exposed palladium films were obtained before the protective coats of vitreous
enamel and paint were applied. One of these resistors was coatedrwith paraffin
and placed in an air cooled hole in the Oak Ridge pile. A fifteen-hour ex-
posure at full power reduced the resistance from 48,300 to 234 ohms. A
similar resistor in a chamber evacuated to approximately nine microns showed a
resistance change of from 51,000 to 252 ohms within two minutes after 44 centi-
meters of hydrogen was applied to the system. The resistors were maintained
at approximately room temperature during both the proton-recoil and hydrogen
gas experiments.

The palladium film resistors normally exhibit a negaeive temperature
coefficient of resistance. After bombardment with r6001l -protons, oOr exposure
to a hydrogen atmosphereg the temperature coefficient ofre51stance is positive.
Investigations of R. H. Kernohan? show that a palladium wire will absorb

approximately two hydrogen atoms per atom of palladium. The effect is to in-

~crease the resistance by a factor 1.735and increase the length by approximately

3%. On the basis of the above information, the following mechanismis suggest-
ed. The thin palladium film i1s non-uniform on the rough ceramic surface, and
this is so to the extent that the resistance depends largely on the cross
section of many small contact points in the metal film. In the normal re-
sistor thermal expansion brings the large metal surfaces adjacent to these
contact points closer together, increasing the cross section at the junctions.
In this manner a negative component of the temperature coefficient is provided
which normally OVerrides'the intrinsic positive coefficient of metal palla-

dium. When the hydrogen is occluded in the palladium, an analogous expansion

w1th1n the rough metal film permanently increases the cross section at the
'gunct1ons and reduces the resistance despite the accompanying increase in re-

‘ ?s1st1v1ty. Hav1ng become more homogeneous, the film exhibits the temperature

'coeff1c1ent of a metall1c conductor.

This phenomenon was first obserVed in the fall of 1947 at Argonne National

Laboratory, when NEPA conducted radlatlon damage tests onelectronic components

under the direction of Mr. E. S. Bettis and Dr. E. R. Mann. In these tests, and

again recently at the Oak Ridge pile,thevitreous enamel covered palladium film

4'Notes on the Charging of Palladium with Hydrogen’. R. H, Kernohan, Memorandum Report PL-MR-1, E. E.

Dept,. University of Illinois, Urbana, I11.

16
o e B i A el xR

o i Ly o

o

KRR e i G .

with a proportlonal counter.

'good agreement with measurements made at NEPA.

resistors of Continental Carbon were exposed in jackets of paraffin, poiystyrene,
graphite, cadmium and aluminum. The resistance decreased substantially in the
case of the hydrogenous covered resistors, sometimes to 4% of the initial
value. The agreement in the results between resistors of the same value ex-
posed under identical cofiditions was poor, and it seems probable that this was
due to variations in the thickness of the protective vitreous enamel. Under
the same bombardment the resistors covered with graphite, aluminum and cadmium
did not suffer an appreciable change in resistance.

A resistor which had been irradiated within polystyrene so that its re-
sistance had been reduced to 16,500 from 50, 000 ohms was removed from the
polystyrene, and placed within a thick aluminum jacket, and irradiated agalin
in the Oak Ridge pile. 1In six days the resistance had dropped to 1,200 ohms.

The Argonne tests also show that when a paraffin coated resistor is placed

‘within the pile, the resistance commences to fall only after the pile power is

brought up, but after the pile is shut down, the resistance continues to. de-
crease. Apparently once a resistor has been bombarded by recoil protons, a
migration of the hydrogen trapped within the ceramic is sustained by gamma

radiétion after the neutron flux is cut off.

NEUTRON ENERGY SPECTROMETER

B, R. Gossick®, K. Henry™, Technical Division

The NEPA proton recoil neutron energy spectrometer has now been installed

at ORNL (Fig. 1). Protons emerging from a hydrogeneous radiator are detected
The counting rate 1is recorded with different

thicknesses of alumlnum absorbere 1nterposed between radiator and counter, and

the neutron flux dlstrlbutlon in energy is obtained by a mathematical analysis

. of these datao Callbratlon measurements with Pu?®® alpha partlcles in a

proport10na1 counter de51gned ‘for an average collimation error of 2.7% gave
A similar counter is now being

built in wh1ch resolution is sacrificed in favor of increased sensitivity.

This tube.wlll have an average collimation error of 9.1%.
Table 1 has been calculated to illustrate the order of resolution which
can be obtained with this instrument. The first column gives the number of

counts per hour to be expected. per cem? of radiator, when the instrument 1is

# NEPA personnel. 17
 

i
3

 

 

 

 

PHOTO NEPA U 30882
_ - | NOT CLASSIFIED

 

 

 

FIGURE 1. NEPA PROTON RECOIL DETECTOR ASSEMBLY
Protons from the hydrogeneous radiator (2) are detected in the proportional counter
(1). The counting rate is recorded with different thicknesses of aluminum absorbers
(3) interposed between the radiator and the counter. From these data the neutron

energy distribution is inferred. In this photograph the instrument 1s being cali-
brated with neutrons from a Po-Be source (4).

. ' . 18 .
TABLE 1

Energy Resolution in the Neutron Recoil Spectrometer

 

COUNTS PER cm>

AVERAGE ERROR

ENERGY SPREAD

MEY ENERGY

 

9.0

 

19

 

 

pery hg COLLIMATION RADIATOR INTERVAL
1.0
026 /cb(E) dF 9.1% 10% 0.8 - 1.0
0 8 - -
5.5
156 /cp(r«:) dE " " 4.5 - 5.5
4.5
11.0 N
.38 /¢(E) dE " 9.0 - 11.0
9.0
10
0066 /qS(E) dE 2.7% " 0.8 - 1.0
0.8
5.5 |
040 / (E) dF " 4.5 - 5.5
4.5
10
096 [ $(E) " 9.0 - 11,0
placed in a neutron flux J/ré (E) dE. From this the standard dev1at10n can be
obtained, after a choice is made of the time which can be allowed for a de-
sired count and of the area over which the flux can be measured.

Calculations of energy spread due to thickness of the hydrogenous radiator
are based on the stopping power calculations for paraffin by Hirschfelder and

Magee (MDDC 115). However, polystyrene radiators are being used because of

»thelr more uniform thickness. Pre11m1nary measurements of the relative stop-

ping power of polystyrene, made by Mr. Keith Heflry, indicate that 1.2 mg/cm®
thickness of polystyrene is equivalent to 1 cm of air, which checks within 6%
of the corresponding value based on the proton- -energy curves of L1v1ngston and

BetheJ Rev. Mod. Phys. 9, 245 (1937) for air, and the tables of Hirschfelder

and Magee for paraffin.

SHIELDING MATERIALS

T. Rockwell, Technical Division

Pb-B-H,0 System. It seems reasonably certain at this time that a nearly mini-
weight shieldwill conrsist of a heavymetal, hydrogen, and boron. Lead seems to be
enough better than iron and not urequivocally inferior to tungsten, gold, and
other more exotic materials so that attention can be profitably focused on it
for some time to come. Boron and B,C (80% B) have very similar properties and
the latter, costing only 2% as much as boron, can be used as a stand-in for it
in fabrication studies. Hydrogen has been the subjeet of considerable in-

vestigation: hydrides, hydroxides, hydrates and organics have been studied at

- NEPA, " in thls group, and elsewhere. Most of them have little more hydrogen

.denslty than water, and the problem of stability under operating conditions of

temperature rad1at1on and atmosphere, is a serious one, Water, flowing
through a lead-boron compact, makes a shield which is radistion-stable, heat
d1351pat1ng, and reasonably easy to fabricate.

Therefore, pre11m1nary explorat1on of the Pb-B-H,0 system was begun th1s

Aquarter. A ternary diagram, ‘with lines of constant den31ty (Fig. 2) ‘shows the

possibilitiesof the system. Several methods of fabrication suggest themselves.
Lead and boron can be co- pressed hot to form a material similar to "Boral.

Several such compacts were made, and cooling channels were placed in some, to
give a shield specimen approxlmateiy 15% H,0. 30%'8, and 55% Pb by volume.

20
n” s

 

 

 
  
 
  
    
    

=0 L j’o
% (VOL) Pb

FIGURE 2

DWG. 81sh
NOT CLASSIFIED

DENSITIES OF Pb-B-H20 SYSTEM

2250
2= 100

i

 

 
ikl e

Rk . ekl a L. G Gkl

Somewhat higher boron concentration and, of course, any water fraction can be
obtained. It is believed that similar systems could be built up of tungsten

rods flash-sintered together, with water cooling channels between them, and that

metallurgical grade B,C "gravel™ could be used with mercury cooling. The

stability of such systems, contrasted with chemical compounds, is a marked ad-
vantage. :
Boral. The 250 sq ft sheets which were to be rolled at Lukens Steel Co.

this quarter were delayed by the steel strike; and are now scheduled for com~

pletion during_November. Some difficulty has been encountered in fabricating

" specimens for the precise thermal conductivity tests, but it is hoped that

this will be completed this quarter. The irradiation of three tensile speci-
mens has been completed up to nearly 4 X 10*® nyt (three months in the ORNL
isotope stringer) and the only change has been a continuous increase in
strength, up to 150% of the original. New specimens are being irradiated and
a request for irradiation at Hanford has been filed. This material seems des-

tined to play an important role in many reactors and a report covering the

.above three phases will be 1ssued soon, to supplement ORNL 242, the first

top1cel Boral report
One of the group has been working at NEPA, learning new techniques of

hot-pressing and other fabrications appropriate to boron and boron carbide in

combination with soft metals such as lead and aluminum.

The first irradiation specimen of "Boroxal™ (B,0, and Al) does not seem
to be faring as well as Boral, which is not surprising, since B,0; is the
continuous phase in the former, whereas Boral derives its structural strength
from a continuous aluminum matrix. The Boroxal specimen showed a significant
decrease.nistrength which w111bereported after later specimens are examined.

Boron Plasttc A m1xture of clear Tygon (a plastic paint) and B,C has

__been ‘made to form a sheet mechan1cally similar to leather, contalnlng 50% B by

volume. ‘Sheets five feet square and one-eighth inch thick are being fabricated
for the lid-tank attenuat1on test1ng facility, to study the effect of coating
the metal in e metal-water system, with a thin coat of boron to absorb the

neutrons which have been degraded in the metal and immediately thermalized

‘Jiln the water-; These sheets can be glued to 1ron, lead, or tungsten sheets,

and removed at will, 'They are strong, light, and flexible and should £1nd use

in many places throughout the project. A top1ca1 report will be written,

22
o b i

Boron Production and B*° Separation. The literature was surveyed and a
few runs were made to produce BCl, from B,O, with HCl and a dessicant, and
later with Cl, and C as chlorinating agents. Temperatures up to 1000° F were
tried without interesting yields and the project was shelved for lack of man-
power. At the request of this section, some rough caleulations were made by
R. Zirkind of BuAer, USN, of the effect of increasing the B!? .content in a
boron shield. Preliminaryrresults are encouraging and the survey of the
possibility of producing cheap tonnage-lot B'° was also promising.

| Concretes. Of general interest to reactor technology is the work on con-
cretes. Laboratory tests on barytes concrete (density 3.5) for hot laboratory
shielding have been completed by the group and by the Skidmore-Owings-Merrill
teeting staff. Field tests have been carried out by J. A. Jones and the Austin
Company, ahd'results at this date seem very satisfactory. A topical report
will be issued by ORNL Engineering Division. | -

' Several trial pours of MO concrete test slabs, 3 in. X 56 in. X 66 in.
for the attenuation testing facility, have been made, with increasing success
each time. Vibration placement, as is planned with field pours, has been made
possible by procurement of a small electric internal vibrator. A satisfactory
technique now appears to be available and will be used when samples are re-

quested by the attenuation group. Density can be varied within quite a wide

range (~ 5.0 to 6.3 g/cc) by varying the ratio of steel punching to steel

curlicues (turnings), which prevent the punchings from packing as compactly,
Densities up to 7.0 are anticipated (if desired) on thicker slabs.

Work on silica gel (97% H20) was continued, then shelved for lack of man-
power. If kept wet, silica gel seems to have most of the desirable properties
of water (high- hydrogen content thermalstab111ty probable radiation stability,

- negligible ‘cost) with some mechanlcal strength Various tests, with and with-

out aggregate,‘were performed.

Aggregate studies, including cost, availability, density, and strength
of concrete, were run on ‘Birmingham 11mon1te ‘Montana taconite, and Tennessee

barytes _
Steel br1cks have been ordered for shielding the MTR Mock-Up. Samples

2 in. X 4 1n.'>< 8 ‘in. 7W1th Varlous surface treatment are also being prepared

as poss1b1e alternates for lead br1cks Intens1ve follow-up on cost estimates
have lowered the price from $9.00 to $1,45pm1'br1ck, in quantities, delivered.
Fundamental work on concretes and cements was continued at a very low

manpower level. Shrinkage and expansion tests, aggregate grading calculations,

23
A

moisture content under different conditions of temperature and humidity, are
being studied. |

ORNL 243, an extensive survey of cheap shielding materials, is being
issued. A "final"-fepbrt on oxychloride concretes will follow. The material

originally written for the special shielding issue of Nucleonics is being

published as a classified report prior to declassification.

24
it

)

HEAT TRANSFER

Technical Division

Work on heat transfer during the past quarter has included an abridgment
of ORNL 156, a theoretical study of heat transfer in annuli, and a small ex-
perimental study which disproved the existence of "polarized turbulence™. The
physical properties which control the heat transfer characteristics of molten
sodium hydroxide have also been invesiigafiedu Experimental liquid metal heat

transfer studies, which were inactive this qfiarter will be resumed next quarter.

HEAT TBANSFER SUMMARY
W. B. Harrison*
The summary of atomic energy heat transfer work, OENL 156, has‘béen

brought up to date and abridged for publication as an unclassified document.

It was felt that much of the information contained in the original report

should be made available to industry and the entire engineering field. This

was impossible in its'original form, but by deletion and rewording, the major
portum1hasbeen converted to a useful source book which discloses no classified
information. The revised manuscript 1s being given its final- editing, and

then will be submitted for declassification.

HEAT TRANSFER IN ANNULI

R. Bazley

Heat transfer in annulx was studied by Dr. Raimond Bailey who was on
leave to the Laboratory this summer from the University of M1ss1s31pp1 through
the Oak Ridge Institute of Nuclear Studies. As a result of his work ‘a new
heat transfer relat10nsh1p is available which satlsf1es exper1mental results

with liquid metals for the first time for all cases where 11qu1d wets the wall.

' The studies have important implications for heat transfer in annuli with all

fluids. In the course of his investigation it was necessary for Dr. Bailey
to develop a knowledge of the flow distribution in annuli with very meager
data. A final report on this work will be issued shortly as ORNL 521.

® Consultant, from Department of Chemical Engineering, University of Tennessee-_

925
Sl e sk

. momema

e o b B L

b e e i, LG M e

- i

#

®

Bailey’s equation is:
Nu = Nu_ + .0106 R-®7 (Pe)-®® |
whe re

1/Nu, = {1/[8B®+1)2]} [-3-123e1432-453+4(3 + 1) 1n R].

-t
o

= Inner radius of annulus divided by the dif-
ference between inner and outer radius.

R = Outer radlus d1v1ded by inner radlus of
annulus.

 POLARIZED TURBULENCE
E._Sparfow

Reports by_bther investigators have indicated that under certain condi-
tions the turbulefice in rectangular channels of large width to thickness ratio
might be polarized; that is, the turbulence might occur only in planes parallel
with the width of the channel and having no component parallel with the thick-
ness. Should polérized turbulence be possible a way would open for a number
of fruitful hydrodynamics studies. Experiments were conducted to prove or
disprove this conclusion, and it was found that no polarized turbulence occurs.
In addition, it was. found that the mixing depthwise in the channel occurs at
approximately the same linear rate as does the mixing across the width of the
channel Photographs of ink threads in the channel from two points of view
were obta1ned 51multaneously which illustrate the result of the exper1ment.

The report ORNL 471, has been issued coverlng ‘this work.

PHYSICAL PBOPEBTIEq OF MOLTEN SODIUM HYDBOXIDE
A S Kttzes |
..1hégfég€xifi}IéfigfauNQOHf£é édbi1é'éoolfiht has raised the question as to

its heat transfer characteristics. A review of the literature revealed data

on the density and viscosity of liquid NaOH, but no data on thermal conductivity

or heat capacity. Therefore, the thermal conductivity and heat capacity for

liquid NaOH were determined experimentally. The data are summarized in the
following table. Density and viscosity data which were abstracted from the

literature are also included as referénce material.

26
»
o —

 

 

 

 

 

 

 

oy | g | e m | Em ey mmanan]
1.786 320 4.0 350 1.0 720- 0.27 ]800-1000
1,771 350 2.8 400 , 900
1.746 400 2,2 450
1.722 | 450 1.8 500

1.5 600

 

 

The density and viscosity data were determined by Arndt and Ploetz,
Z Phys. Chem. 121, 439 (1926).

The reported values are averages of a number of runs and are believed
accurate within 20%. The set-up for the thermal cenductivity measurements was
calibrated by determining the thermal conductivity of water at 95° C. Good
agreement was found between our values and those reported in the literature
for water. The heat capacity set-up was checked by determining the specific
heat of lead. Again good agreement was found with reported values.

The'heat transfer coefficient of ligquid NaOH was not determined. However,
the coefficient can be predicted approximately from Lyon’s equation (ORNL 361)
for high Beynolds number and from the Dittus-Boelter equation for low Reynolds’
number. - _ |
| It was.also noticed during the course of the thermal conductivity and heat
transfer experimehts that liquid NaOH in the presence of oxygen corrodes 303
"and 304 Stainless Steel. Fe,0, was found in the NaOH and also, green and
yellow deposfts were found on the walls of the equipment. The NaOH apparently

attacks and removes the chromium from the stainless steel.

THE LIQUID METALS PROGRAM FOR ANP
R;.Nn‘LyOfi

One of the prOposed systems for reactor powered alrcraft is to transfer
the heat generated in a nuclear reactor to air passing through a turboget
engine by circulating a liquid metal. The development of such a system can be
broken down into a number of problems which are listed below, not necessarily

in the order in whi ch they should be attacked:

27
bt Gab L bk R

-«

-«

1. Selection of liquid fietal;
2. Selection of container and component materials;
3. Development of handling and flow control methods,
a. Pumps, |
b. Valves,
c. Pipe Joints; B
4. Study of heat transfer characteristics of liquid metals;
5. Preliminary desigh of system;
6. Mock-Up and testing of preliminary-design;
7

Final designQ

The selection of the liquid metal appears to be between bismuth or lead-

~bismuth alloy and the mass seven isotope of lithium. Other possible contenders

have been eliminated largely on the basis of their induced activity which would
require shielding of the piping and liquid—to?air heat exchanger.

The selection of container materials must be made on the basis of high
temperature strength and corrosion resistance to the ligquid. In addition,
materials to be used in the reactor itself must have a low capture cross section
for neutrons. | |

The development ofpunms for'thlssystem involves a number of considerations
not previously encountered. Electromagnet1c pumps, which show considerable

promise in handling sodium and sod1um-potass1um, are less efficient when used

for lead-bismuth or lithium, because of the lower electrlcal conduct1v1ty of

these liquids. In addition, large electrical generating equipment will be re-
gquired while mechanical pumps can be driven directly by a power take-off from
the turbojet rotorfl Thus it appears that mechanical pumps are to be favored
over the electromagnet1c type. '
‘While conslderable progress has been achzeved at other 1nstallatlons in

the development of pumps for 'sodium alloys at high temperatures, the con-

' 31derat10n of lxghtness, compactness, and the hlgher temperatures required to-

ether w1th the attack of nzckel alloys by lithium and lead- bismuth, 1nd;cate
the need for a relat1vely 1ndependent program for ANP. '

To a large extent, the development of a suitable mechanical pump depends

on’ the development of sultable bear;ngs and/or a su1table shaft seal. It is

in this direction that work w1ll first proceed

The same 31tuat1on applles to the development of valves and pipe joints,

'although to a lesser degreeor Temperatures up to 1800° F are currently being

considered for the aircraft power plant, while temperatures«:fonly 1000 to

28
”»

1200° F aré-planned in other liquid metal cooled reactors. As a result, more
intensive development is needed to provide satisfactory—solutions'to the
valving and joining problems in the aircraft system.

To work on these mechanical handling problems, a new group is beihg set
up in the Technical Division. Space is being set aside and technical men are

being recruited for this work. Study of the heat transfer characteristics of

liquid metals is being resumed with increased emphasis, both on a theoretical

and on an experimental basis.
The liquid metal heat transfer group is being enlarged and design of a

relatively high pressure-high flow heat transfer system will be started almost

immediately. The theoretical study of liquid metal heat transfer, which has

proved remarkably fruitful in the past, will be resumed and intensified. Close
liaison will be maintained between the theoretical and experimental work,
however. | |
Design and construction of a Mock-Up of the heat transfer system at one
of the cooperating.sites will permit testing of the components under more
nearly true operating conditions as well as determining conclusively the

feasibility of the overall system.

29
¢ e S B e e s

»

METALLURGY AND MATERIALS

J. H. Frye, F. Kerze, E. C. Miller; Metallurgy Divisién

The Metallurgy Division is undertaking the development of aircraft reactor
materials for use at high temperatures in the presence of liquid metals or
other potential coolants. Close liaison is being maintained with NEPA to
coordinate the programs and to avoid duplication of effort. It is believed
that this Division can make its most effective contribution by concentrating
on fundamental liquid metal corrosion studies, mechanical testing of materials
in molten metals at elevated temperatures, and investigating the fabricatioen
and cladding of selected materials.

In the initial phases of this work, selected-elements with high temp-

‘erature possibilities—-iron, nickel, cobalt, molybdenum, chromium, zirconium,

titanium? beryllium, tungsten, tantalum, columbium, vanadium, and silicon-
will be corrosion tested inmolten lithium and in molten bismuth at 1800-2000° F
and higher, to effect a sorting on the basis of relative corrosion behavior.
The work may be extended later to include other coolants such as lead-bismuth
alloy, sodium hydroxide or gases.

On the basis of the preliminary tests, the more promising metals and their
alloys will be subjected to quantitative corrosion tests to investigate the
influence of such factors as atmosphere composition, contamination of liquid
metal, surface condition, wetting behavior, and dynamic corrosion.

The selected metals and their alloys will also be investigated to deter-
mine their high temperature mechanical prepertiee and the feasibility of their
fabrication. This will involve creep and stress-rupture tests in liquid metal

and'othef environments, as well as methods of shaping, welding, and other

_means of 301n1ng -MerBaentm’ehd’ldfi carbon iron already appear to have good

corros1on re31stance in bismuth, and probably in lithium. Because of this and
its high- temperature strength, molybdenum will be the first metel'studied in
this manner. The unfavorable h1gh temperature oxidation behavior of molyb-
denum will also require corrosion 1nvest1gat10n at low oxygen pressures, and
a study of the posslblllty of reduc1ng this oxidation by addition of alloy1ng
elements° AR B '

" The ideal constructlonal materlal would be a 31ng1e metal or alloy pos-

‘sessing a combination of hlgh temperature strength? oxidation resistance, and

freedom from corrosion by the liquid metal coolant (plus, of course, the de-

sired nuclear and heat transfer properties). Every effort will be made to

30
Al GRS B

ARl walaok Anao . .

e B MLy e

*

i

find such a material, but recognizing that this may not be possible, concurrent
efforts will attempt to develop a composite material in which a protective
coating of a coolant resistant metal is applied to one of the more conventional
or recently developed high temperature and oxidation resistant alloys. Dif-

fusion, forming, and joining of these composite materials will also be in-

vestigated.

In the first experimentél work, immediétely available materials have been
used to set up a resistance tube furnace in which specimens can be corrosion
tested in a crucible of molten bismuth at about 1800° F in either vacuum or
argon. This furnace is not adaptable to lithium. |

Preliminary qualitative tests were made, primarily to establish furnace

‘techn1ques, using beryllium, nickel, and stainless steel No. 309. Beryllium

appears to have good resistance to molten blsmuth nickel, as was expected,
dissolved completely; and S.S. 309 showed some signs of attack. However, the
set-up proved cumbersome; the maximum attainable temperature was too low, and
the desired variety of samples was not 1mmed1ate1y avallable.

Efforts are now being concentrated on a procedure to charge the specimens
into sealed evacuated iron capsules containing the coolant metal. The capsules
will then be charged into a conventional tube furnace with available tempera-
tures up to 2500° F. This should be in operation by the first week of December.

Steps are also in progress to design and build suitable equipment for
wettability tesfis, controlled atmosphere and dynamic corrosion tests, and
stress~-rupture and creep investigations.

Three of the Laboratory’s consultants, Professors E. C. Creutz of Carnegie

‘Instltute ofTechnology, J. L. Gregg of Cornell, and N. J. Grant of Massachusetts
-Instltute of Technology,_are act1Ve1y as51st1ng in the collection and eval-

uation of data on the fabrlcatlon and claddlng of high- temperature alloys for

reslstance to llquld metalsa

31
At PR MM aBE . . e

P

oo B et

L R

>

RADIATION DAMAGE

" D.:S. Billington, Metall&rgy Division; M. Bredig, Physics Division

BEACTOR CORE MATERIAL STUDIES

Personnel. The Radiation Damage group of the Laboratory has had a group
of75 men from NEPA for well over a year. In the course of this time they have
acquired coneiderablevexpefienoe in various aspects of radiation damage, such
as radiation hazards and safeguards, hot laboratory operation, design and
operation of remote-controlled apparatus for use ina hot laboratory, techniques

for "din pile" experiments, cooperation in design of "in pile" experiments,

~investigation of radiation effects in certain selected materials, and an in-

troduction to the theory of radiation damage through lectures by various staff
members, plus a current lecture series by Dr. Evans on Solid State Theory. In
addition to practice 'in the use of a nuclear reactOr,_SOme of the trainees have
gained experience in designing experiments for supplementary studies using
accelerators such as the Van de Graaff and the cyclotron. Finally, some of the
trainees have participated to some extent in the design criteria for a new hot
laboratory facility. | |

~ In a recent augmentation of this training program, three additional men
from NEPA will join the staff of the Laboratory. The above training program
has engaged the attention of meny of the ORNL group and has involved all of
them at one time or another. It is a pledsure to acknowlege that the NEPA
personnel have contributed in large measure to the solution of numerous prob-
lems of the ORNL Radiation Damage Program,

Cooperattve Program - NEPA has been 1nvest1gat1ng certain ceramic com-

binations that appear fea51ble ‘for use ‘as fuel elements, prov1ded the elements

will hold up under reactor condltlons "ORNL has undertaken to make radlatlon

damage stud1es on these proposed fuel elements. The first ceramic body now

‘under test is berylllum-carblde (the moderator that ult1mately is expected to

be comblned w1th uranlum compounds to make up the fuel element for the air-

"cooled reactor) It 1s 1mportant to learn if thls materlal w1ll prove suit-

able, as its other properties appear excellent.
Prellmlnary experiments are underway in the ORNL reactor studylng the

electrical resistivity during irradiation and such properties as modulus of
elasticity, hardness, and coefficient of thermal expansion before and after
irradiation.

32
e B, B

- A NEPA-designed thermal condfictivity apparatus is at present being studied
in the ORNL reactor. This and similar experiments will serve as feasibility
experiments for more elaborate experiments méking use of the Hanford Reactors.

Exposures of Be,C bodies to Hanford flux will be made in the near future.
These bodies will be studied before and after irradiation at Hanford. Pro-
perties to be measured are: stored energy, modulus of elasticity, annealing
charactepietice,‘coefficient.of thermal expansion, dimensional stability,
surface effeets.(semi-oonductor broperties) and thermal conductivity. Should
the demage'eharactefistics of Be ,C appear suitable, then UQ, and/or UC will
be added and the mixture studied as an active fuel element.

The complete program calls for the study of a number of p0351b1e compo-

nents for fuel elements, each of which will eventually be studied both sep-

~arately and together. A fuel element normally consists of three essential

components: the fuel, the moderator and the coating. The study of the best

form (physically and chemically) for each of these is a complex problem and

involves an immense number of variables. Combinations under consideration
are: _

1. Carbon bonded graphite - uranium bodies

2. Beryllium carbide matrix - uranium bodies

3. Metal-ceramic bodies containing uranium

4, Beryllium oxide matrix - uranium bodies

5. Materials above plus suitable coatings such as iron-chromium

or metallic Si.

To augment this essentially engineering approach, the ORNL group plans
to make a study of the general problem of high temperature damage. It is felt
that single’cr?stal studies should be particularly useful; not only of the

‘materlals mentloned above, ‘but also of compounds that may lend themselves more

read1ly to exper1mental manlpulatlon Also, the data may be more amenable to

theoretlcal and practlcal 1nterpretat10n. These studies would include me-

tallic systems .
In addition, experlments with the Van de Graaff accelerator are underway

w1th the obJect1ve in m1nd of studylng separately the various types of damage
to be expected | o ) ' | |

Facilities. The following facilities are available to the ANP Radiation
Damage Proéram: - o | ‘

1. The X-10 reactor

9. Hot laboratory in Building 105
3. Hot chemistry cells in Buildings 706-C and 706-D

33
M g G AR

o T i

-

)

4, The Van de Graaff accelerator - electron and proton beams

5. PBrookhaven reactor - an investigation of the practicability of
using this reactor has been made and when this reactor is in
service, use will be made of certain fac111t1es

6. Hanford reactors
7.  Metallographic and fabrication facilities of the Metallurgy Division

8. Shop facilities in Physics Building, Metallurgy Building, plus
general Machine Shops.

AUXILIARY MATERIAL STUDIES

0. Sisman, C. D. Bopp, Technical Division

Metal Hydrides;_ In'cbo?eration with NEPA, the radiation induced dis-
sociation of titanium hydride was determined by domparison of the dissociation
pressures obtained under radiation with those obtained'under normal conditions
for a series of temperatures.

- The apparatus consisted essentially of a furnace for heating the sample
above normal pile temperatures, and gauges for obseryihg‘the pressure. A
sample of stoichiometric titanium hYdridé (TiHQ) contained in a stainless
steel reaction tube was placed in the furnace, which was then inserted in the
pile. Small bore tubing was used to connect the reaction tube to the gauges
outside the pile.

After the apparatus had been evacuated and flushed several times with
purified hydrogen measurements were begun. The furnace temperature was main-
tained at a constant value and the sample allowed to decompose until it appear-
ed that equlllbrlum was established. Observations of the dissociation pres-
sures were made in this manner over the-temperature range from 160° C to 340° C
during 1,800 hours in the pile at an estimated average flux of 0.5 x 10*?2

neutrons/{cm?) (sec). | ,
Results indicate that little, if any, radiation-induced decomposition

.bccurred with this hydrlde.'

Slmllar experlments are now underway to determ1ne the effect of pile

radiation on the stab1l1ty of lithium hydr1de and zirconium hydrlde, and to

get further data on two compos1tlons of titanium hydride (TiH, ,¢ and TiH, ).
Plast;cs._ The changes in physical properties of commercial plastics are
being studied because of the desirability of plastics in reactors as instrument

insulators, flexible tubing, protective coatings and components of experi-

34
o o e AR R M LML L AR

L L o e

e e L M ki

i R o S R

"

mental and testing equipment. The importance of this program has increased

greatly with the possibility of radio and electronic controls in the relatively

intense radiation field in proposed remotely controlled mobile reactors.

Quantitative information on the tensile strength impact strength, elastic
modulus, percent elongation, hardness, density, and water abeorption after
var1ous irradiation dosages in the OBNL reactor has been obtalned for a wide
range of commercial plastzcs, and these tests are continuing in order to
provide sufficient 1nformat10n for graphs of propert1es versus dosage for all
of the materials. ‘ , .

7 Electrical_properties such as'resistivity, dielectric strength and arc
resistance are also being determlned '

Table 2 provides an indication of the wide range in the resistance of
various plast1cs to irradiation by‘neutrons. Except where the material be-
comes unusable the ratings in this table are based on change in strength with
radiation rather than actual strength. Thus for a given purpose Bakelite re-
inforced with paper or linen might be preferred to polystyrene, even though
the latter undergoes essentially no change.

The following plastics crumbled after irradiation by 10*® n/cm?:

Casein

Cellulose Acetate
Cellulose Acetate Butyrate
Celltlose Nitrate '
Ethyl Cellulose
‘Fluorothene

Lucite
Teflon

It 1s expected that w1th1n the next four to six months, suff1c1ent data

w111 have been accumulatedtx)permlt publ1catnm1ofthe quant1tat1ve information

in a toplcal report Whlch will 1nc1ude graphs and tables to present the phys-
'1ca1 and electrlcal propertxes of plastlcs after a wide range of reactor ex-

posures.

Sodium Hydroxtde Interest:xlsodium hydrox1de as a possible pile coolant
has.ralsed the quest1on of the stab1l1ty of molten sodium hydroxide to p1le
radlatlon. For a gquick exploratory test, six 0.5 gm samples of sodium hy-
droxide pellets were sealed in 3.5 cc glass ampules and placed in the pile.

Three ampules were kept in the pile for one week, and three were kept in for

35
R b b il R W e

- TABLE 2

s wnn el EFEAL e S Bkl i BB -

Change in Strength upon Irradiation

by 1-2 X 10%® pn/cm?

at 40° C

 

RESISTANCE TO CHANGE IN
TENSILE STRENGTH

RESISTANCE TO CHANGE IN
IMPACT STRENGTH

REMARKS

 

Polystyrene

.Styron

Furfuryl Alcohol Polymer
Haveg (asbestos and Bakelite)
Nylon

Poly Ester Plastic

Allyl diglycal carbonate
Vinyl chloride Acetate.
Melamine Plastics

Bakelite (baper reinforced);

Bakelite (linen reinforced)*

Saran

 

Excellent
Excellent
Excellent
Good

Excellent

Excellent

Poor

 

Excellent

Good
Excellent
Fair

Fair

Excellent

Good

Poor

 

Initial tensile strength
low, but increased by
factor of 5 on irradiation.

Initial tensile and im-
pact strength very high
after irradiation. Impact
strength similar to poly-
styrene. Tensile strength
higher than polystyrene

Unlike most plastics, Saran
softens on irradiation.

Excellent - essentially no change; Good - reduction by less than 50%; Fair - reduction by more than 50%; Poor - unusable after irradiation.

® Presence of water during irradiation causes complete breakdown of bakelite.

36

e 1 e B, T vl e IR s e e . . i

- b .

AL, ek
e B e M e b £ M M

&

four weeks. The one week samples showed no gassing, but the 4 week samples
produced a considerable quantity of gas. Results are given in Table 3.

These samples were not molten during irradiation, but, for each set of
three samples, one was melted before sealing the ampule, one was melted after
irra&iation, and the third was not melted. All three ampules were sealed at
atmospheric temperature and pressure. The samples were tested for gassing by
breaking the ampules in a sealed container and measuring the volume of escaping
gas on a manometer. | \ T

Fast Flux in Hole 19. To compare the radiation damage done in Hole 19
of the ORNL reactor to the damagé done in other reactors it is necessary.to-
know the neutron flux spectrum in Hole 19. This spectrum (Fig. 3) has been
determined by a method employing threshold detectdrsa From this spectrum the
fast flux (abofie 1 Mev) was evaluated as 0.11 neutrons/(cmfi)(sec)(watt) The
epithermal flux was evaluated by a method employlng cadmium ratios, as 5.3 X
10% neutrons/{cm?)(sec)(watt).

Threshold detectors are isotopes that react only with neutrons having
kinetic energy above an individual threshold energy for the detector. Above
this threshold energy the probability for the reaction increases until it
reaches a constant value. The effective energy for the reaction is the ficta-
tious threshold energy arrived at by assuming that the cross-section curve
has a square cut-off at a minimum energy, instead of the actual gradual de-
crease to zero. o

The threshold reactions listed in Tabié 4 were employed to plot the

spectrum of Fig. 3 by a method of successive approximations. (This method will

be described in ORNL 525.) 1In Table 4 the average cross section of the isotope
for the flux above 1 Mev is also listed. 1In Fig. 3 the ratio of the specific
flux nvg to the total thermal flux nv’' is plotted against energy. Points are

plotted at the effectlve energ1es of each of the threshold react1ons as given

in Table 4.

The 1/E région of the §pectrum-ih-Fig 3 was determined by the method
given in CP 3781 from the cadmium ratios g1ven in MonC 398. (This method also
will be descr1bed in OBNL 525.) -

The thermal flux in Hole 19 was determ1ned by activation measurements of

'cobalt foils. Seve:al measurements gave an average value of 3.0 X 10§ neutrons/

(em®)(sec)(watt). | o
High Intensity Gamma Source In order to intelligently design reactor

auiillarles, electrzcalcontrolsystemsandtmdiobhemical processing equipment,

37
TABLE 3

Radiation Stability of NaOH

 

 

THERMAL NEUTRON THERMAL FLUX GAS PRODUCED cc/gm
DOS AGE [a/¢em® yisecy) . AT 25% ¢, 760 mm Hg
SAMPLE n/cm’ )

Melted before irradiation | 1.35 x 10*’ 0.27 x 10%? None
Not melted b 135 x 1007 0.27 x 10°? None
Melted after irradiation‘ 1:35 X 10*7 e 0.27 » 10** o - None
Melted before irradiation | 5.80 »x 10*7 | -O¢27 x 10*%2 ' ‘1958
Not melted | | 1 5.80 1017 0.27 ><.10"“2 | 67.,5'
Melted after irradiation | 5.80 x 10%7 0.27 x 10°7 ampule explodéd while being heated

 

 

 

38
SPEGIFIC FLUX/ UNIT MEV

nvE
nv'!

3

 

0.00! }

THERMAL FLUX

0.10

C.Ci

.
"E- TO
THERMAL ENERGY

 

. FISSION
' SPECTRUM

 

0.1 — | 1.0
| '.VENERGY——MEV
FIGURE 3 NEUTRON SPECTRUM FOR HOLEI9
| ORNL REAGTOR
35

- 10.0
S

TABLE 4

Reactions Used to Determine Fast Flux

 

 

the pile spectrum

curve

 

 

40

 

 

EFFECTIVE RATIO FOR :
THRESHOLD O’-av IN BARNS THE PILE SPECTRUM REFERENCES FOR
i IN MEV FOR FOR PILE OF THE FLUX ABOVE CROSS-SECTION
REACTION PILE SPECTRUM SPECTRUM 1.0 MEV TO THR DATA
THERMAL FLUX
A1%27 (n, o) Na2* 8.1 0.0010 0.039 CF 3574
"Mg?* (n, p) Na** 6.5 0.0017 0.035 o,
- A1?7 (n, p) Mg®’ 4.5 0.0035 0.033 "
§°2 (n, p) P2 3.1 0.14 0,022 LA 515
PP (n, p) Si®? 2,7 - 0,029 0,042 MDDC 360
By integration of 0,036
B KRERL oo

heel

a knowledge 1is needed of the effect of gamma irradiation free of neutrons. To

obtain such information, equipment for producing a high intensity gamma source
k  by irradiating cylinders of gold in the pile has been built and is now being

~assembled in the laborétory for testing.

It is ekpected that this apparatus will be installed in the pile and be
in operation befofe_phe first of the year. Gamma ray fluxes above 10° r per
hour are expééteda ' |

Beta versus Gamma Dosage. The effort to correlate beta and gamma irra-
diation4effectsrhasrbeen continued. It is hoped that with such a correlation,
the effects caused by large gamma doéage can be predicted from the behavior
of materials ufidef beta irradiation. This will greatly aid in conducting and

interpreting irradiation experiments using sources which emit both gamma and

~beta emanations.

The experimental tests have now been completed and the correlations for

a final report are underway.

Lubricants (California Reseaféh Corporation). The OBNL reactor has also
been used by the California Research Corporation for an extensive series of
irradiations of special oils and other possible lubricants for aircraft re-
actor accessories, under a NEPA contract. The results of this work are given

in NEPA reports.

41