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Subject NOTES CN MEETING OF FRIDAY, Copy 7 Veinberg |
MAY 12, 1 .
ad Tnstructions Of
By Chlinger ; ,Z(:/ . W
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DEPARTMENT OF ENERGY| DECLABSIFIGATION REVIEW
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= .fi-ge. If pure 49 were used, the concentration of the slurry would be reduced,

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Seriea A . ? Qg

MERTING OF FRIDAY, MAY 12, 1944

. 900-10:0 . hck-209 CENTRAL RESEARCHLIBRARY --
Tl e el DOCUMENT COLLECTION
Presenti Messrs. pemd., Ailisozi,' Siflard, ?;ig;er, Mck, W adnberg. Seita Coopep, |

Mr. Weinberg opened the discussicn on the subject of conversion units.
The question of comversion units ties in closely with pile policy and depends . .
largely on future contingencies. There are two contingencies for which a conver-

sion unit would not only be very useful but almost mandatory. o SIS
A. Assume 49 is a failure. This is not impossible since it is D e
. rumoured that purity obtained to dete is poor. To get high I R
. purity one needs practically an isotope separation so the . G i

Y simpler canversicn undt for 23 production would be very useful. g S ToA
B. Assume 49 is quite useful so that Mr. Urey can enrich metal by . =~ = %
25 to 30 or even A0%. It then becomes a question of economics ‘

and time whether lir. Urey's enriched preoduct should be turned
over to a conversion unit or some isotope separation scheme.

About a year ago, a unit was designed tentatively for producing completely e
enriched 23. (Throughout the following discussion "enriched by" signifles that : ®
the original concentration of isotope in the metal should be multiplied by the 2
percentage indicated, while "enriched to" indicates the total percent of isotope
obtained in the metal.) This design assuded a homogeneous slurry pile using 6 kg
of metal enriched to 103 (600 gm) of 49 or @5. The slurry would require 1.2 tons =
of P-9 of which 75% would be in the pile and 25% in the external pumping system. =~ =
(This design was not calculated indepandently but was interpolated from larger
homogeneous plants to get a wnit producing about 10,000 kw. )

The proposal entails getting 600 gn of 49 per day from W in the form of
metal enriched to 10%. The complete plant would require several conversion units
in series fed consecutively with this W metal, since the useful life of the metal
in each unit would be small. No details were worked out on the introduction of
gthorium. The power cutput of such a series of wnits per gram of 49 vould be very

sbfit it is doubtful whether there would be any practical benefit fram the use of
~pre 4. Unfortunately, the question of making the slurry has not yet been settled.

. Mr. Fermi raised the question of substituting & solution for the slurry,

“agd asked if there were any objections to this. Mr. Wieinberg answered that the

in@.y objection to a solution was that we did not have a solution any more than we

have a slurry.

15

&2 Mr. Vernon suggested that,instead of using 49 in the pile and thaorium in

&fe reflector, a mixture or solution of therium and 49 might be used, but Mr. hein-
érg said that this would make the pile much larger and ur. Fermi felt that it was

@ifipler to use the thorium in the reflector.

- g T'his document contains informasion gug ting the nations)
- - nesptaioatnattu TE e 13:,.* fihe of the
e S el b *3':'} 50: 31 aeiegAes. cransmission
£ 3 o 5 et S Bh-ts™ contents in any diinner to an
=3 unauthorized person is prohibited by law.

th all information
ercon, 1s the pro-

Lod know-how disclosed ther

1‘-‘:ng'
perty of the Universit

ago, and no

y of Chic

Mr. V.einberg pointed uut that one advantage of 23 was that t.he purity
requirements for 23 are much less stringent than for 49. A small conversiom pile b
using surface cooling would produce only 2000 to 3000 kw but this is still a .La.rge
amount of power from a small amomt oi‘ metal, though the metal would requim
frequent replacing. 3 s 3 S art P AN

- Mr. I-‘emi was afraid o£ poiaoning in such a pile alnce t.he fisaion pm-
ducts do not simply vanish but may collect and cause trouble. Mr. heinberg = Z
answered that it would be necessary to remove the fission products continuously
or periodically but that this should no{'. prove too difi'icult as long as the ‘motal
is usedina.alurryorlolntim. G .-i-‘~:

Mr. Hogness asked. how the heat would be ranoved in such a small tmit.
Mr. Weinberg explained that the solution or slurry would be circulated through
heat exchangers. Mr. Franck asked the total weight of such a unit including the -
shields and Mr: 'aei.nberg guzased that it. would be in the neignborhood of 100 tons._

- Mr. Femi asked how long (1. e s to what mnclment. of 23) t.he thorilm
would remain in the reflector in the pile. Ir. Weinberg explained that the thorilm
would be enriched vith 23 to 0.1% becauae beyond that, one. loses the 23 xomed. Gt

wr. Fenni pointed out that the accuuula‘bion of product in t.he t‘xorium :
would require & separation process and asked whether the chemistry of separatim ; .‘
for thorium would be any worse because of its similarity to the rare earths.. . =
Mr. Wigner felt that this would not be a serious problem since they have succeeded A
in separating small percents of product from uranium. Mr. Hogness suggested a- = - = :
siurry of thorium oxide for use in the reflector with the Szilard-Chalmers sepera-~ . .«
tion process for recovering the product. Mr. lieinberg questioned whether we have
any better chance of getting a thorium slurry or solution than we have with uranium.
Mr. Allison reported that the Canadlans are thinking of using thorium in the re- B
flector and using fluorine to remove the uranium in the form of UFg. However, he

feels that the technical di.fficulties mvolved in this process are great.

' Mr., i‘veinberg pointed out. that one advantage of a conversion unit would
be that it is the equivalent of a pilot plant for a P-9 homogenecus plant. MNr. Fermi
said that this is true except that there is much less concentration than in the
latter. Messrs. VWigner and Wednberg then checked and indicated that since there
would be 0.2 gms. per c.c. of metal in the slurry for an unenriched P-9 homogeneous
pile, there is a factor of 10 over the concentration in the conversion unit. M». Ver-

5 .observed that there may also be same difficulty in keeping the material in
c";i;@.do—-'.’.t)lt.mion and that set out may be a serious problem.

> 9 %

=

S x| Mr. Allison suggested that Lir. Ohlinger keep notes on suggested research
° anffeievelopment work which should be started for such a unit. He proposed the follow-
§ yo to start the list:

E Z#54(1) The behavior of solutions and slurries under radiation

E ¥ (2) The recovery of smell amounts of uranium from large amounts of thorium.

] Mr. Wigner proposed the use of uranium-oxalate as a possible form of a

© By “3_5 a solution since it is reasonably scluble. ir. Vdgner's only worry with
3 S

g
t
a

the oxalate was the aroduct.ion of gum but Jr. Hogxess said that carbon monoxide Sl
would be produced which certainly would not cause gumming. However, the carbon~

‘ate might be formed and cause some deposits. Nr. Vieinberg proposed. attanpting e
to obt.ain the oxa.late of plutonfum t.o detemine :lt.s solubility._ T

. The question of us:l.ng tha n'ltrate was. asked by Mr. Wig:er vmo wondered
about the nitrogen absorption but r, Femi felt that as long as the concentra-
tion was under 10% there was no danger. In turn; he proposed a sulphate but "';:,
questioned whether the colloidal sulphur produced under radiatiom might not gum ¥
up the circulation system. I, Vdgner noted that sulphur precipitation might be
prevented by the use of hydrogen sulphide and that this subject should be invest—
igated. Also, he suggested small amounts of sulphuric acid to keep the uranium - Ay
in solution since sulphuric acid does not attac& stainless steel. AT, do A O s

Mr. Homesa aaid tha’o tha decontamina.tion problem ‘should be included in
Mr. Allison's list and Mr. Cooper recalled that ir. Fermi's question of removing -
the fission products from a circulating stream was anothsr problem for the list. -
Also, the handling and recombination of the gases of decamposition should be looked
into. Mr. Weinberg indicated that the latter problem will be common to all water - '+
moderated -piles. Mr. Fermi estimated the gas formation at about 20 liters per - .
second of hydrogen and oxygen. Mr. Wigner reported that experiments of Yr. Allem . -
had indicated that, with some luck, it might be poseible Lo have recombination = . . &
under equilibrium pressure if the gases were kept in the original tank over the -~
liquid but that this question still needs more investigation. Ur. Fermi recalled =~ = .
from early experiments that a radium solution held in a flask with a vapor space. . = .
above it, established its own equilibrium at around 1/2 atmosphere pressure and B s
that the pressure never did go above one atmosphere. This was mostly the resull
of o4 particle activity. Mr. liigner felt that this was good news since the action = "'
of fission particles would be similar, as indicated by investigations of Messrs. - . '
Burton and Allen who found a I* = 0.3 for both fission and e<. particles. MNr. Fermi
said that about 100 volts were required to dissociate the particlss.. He thought
that the process might follow the cycle of foming hydrogen peroxide which would
then be decamposed mto the gases. : ,

vary as the rate of energy liberation and, although Mr. Franck belisved so,

Mr. Fermi did not believe that this was necessarily true and Mr. Wigner stated

that the evidence was conflicting and that this idea was the result of early ex-
periments. With the formation of hydrogen peroxide, the process gives the equil- -
ibrium at 2 certain pressure regardless of the rate of energy liberation. Ur. Franck
felt that since the radiation field was different in the heat exchangers than in

the pile, one cannot predict the gas formation and recombination as readily as in

" a simple experiment. Mr. Cooper asked Mr. Fermi whether the equilibrium pressure l
obtained was independent of the concentration and received an affirmative answer. |
Since idr. Franck was still in doubt about the equilibrium pressure formed over the

-solution, Mr. Fermi suggested that despite the radiologn.st.s assurance that it was,

he would do some experiments to prove or disprove it.

Mr. Cooper asked whether the equilibrimn pressure might be expected to, it

Mr. Weinberg concluded his description of this type of conversion unit
with the opinion that such a unit is fully within the range of possibility of con-
struction by the laboratory itself instead of by an outside contracter. He also
point.ed out once more. that. such a comrersion mit would serva as a pilot: plant i
for a P-9 hcmgeneous pile. R

ur. meinberg t.heu discussed another type" ot canvarsion unit for am‘ dig..{ o2
rerent use. This wonld be distinctly a war plaxxt for l.9 product.im snppoao

carry the concentration further would rpqnire a large plant. The cmcentratiac AT 7
could be carried on further by the Chicago laborstory with a much smaller pile ifi? ARy
it were constructed with just ordinary water. Preliminary calculations for suc!: - el el
reactor indicate a cylindrical pile about 2 meters in diameter by 2 meters high o, iy R e
with an enriched core of cylindrical shape, 88 cm in diameter and 1 meter high. = i % f
The core would contain 3 tons of metal enriched by 33% while the surrounding shell IRy
would cantain 20 tons of ordinary unenriched material. The metal in this pile = «
would be in the form of rods or short sections of rods joined together in a con= *
tinuous jacket to form a long cartridge.. The jacket for either the long one pi I“ S
rods or. the series of short sectiomr would be of aluminum having a thickness of.

the axis of the cylinder and afranged verbically thx;oughou'b. The: met&‘!. in ths»' i e
rods  through the core would- have a diameter of 1 cm while t.bose in the sholl mflct__ __f

the periphery. This would g:!.ve a volume ratic or 3 to 1l for the metal in tha core....
' The spacing of the rods in the core would be 1,77 cm for a square lattice. ' There
would be 1500 rods in the core and scmewhat more than that in the shell, depa:ding
on the grading. The cartridges through the core would contain enriched material «
. in the portion of the cartridge ext.ending through t.he core and ordinary mateflal,jn

the portion extending - it 1.77 cm..

through the shell. The -

i £t Jacketed Rods
sketch at the right in- =~ -
1.771

dicates diagramatically = ot it L o _ ‘
a vertical section through . @-@-@ 43 AERNTEAREE
SuCh a pj-leO v . , ! ': . (ST & r‘T‘ ot o 4 ‘}r‘ = N
Vi g R ! i I B 1 t :

" The best K for " e E””"’h"‘.] ; : g
an ordinary water pile is . '-i-fi ks ,L ! | core |
around 0.97 but,with oaly =~ =« - .40 core AL HTHE e
a slighdy optmetic 3 ". ¥ = i‘: "l“ ~‘(-'4 ', “ € E’ -} : '1‘L }! ;- - --: “‘ 1:". f:;x'.:‘-
assumption of the ratio , i R e L P ESRAY
of fission to capture - v Ordinary L S e
crosa sec'g.ion (which is rah Me’tgl ¥ _ | X3
uncertain), we can assune s ‘ : 88 am. 2 :
e base k of 1.1 for 3 .. ® @ @ | fcore 7 :
enrichment. With a 2 . @ ST A of
loss from aluminum, k be- ‘hre @ ® .

comes 1.075 and -6 o Alt. Lattice
A= =0.1760 x 10 In '
the shell, k would ba 0.95. As a rough estimate, for each atom of 25 deetroyed in

the core, we.can expect about 0.85 atoms of 49 in the core.

For better cocling of the ro'ds ‘and protettion agsinst warping, it may be |
desirable to have fins on the ends of the rods. Mr. Young has made calculations
' erature (this seems reasonable since the film drop is the largest item), we'can = = .
expect around 60,000 kw from such a unit. - However, since the pile is practically

- heat transfer. The caleulations mentioned above indicate a velocity through the-

‘gallons per minute of water through the pile. Mr. Szilard made the suggestion tha
-+ it would be possible to aveid handl- = . oo 0 o A

P e

o "-.;-:‘ T Ret e
ol S N SaTRERe SV
W WL v e 2P % IR Tt
« J - A% S BYEAR
o 3 SO8
D R ! .
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AL A

#

_on the heat transfer which indicate that, assuming a film drop twice that at W .« - -

or 40°, and assuming that the water through the pile is all about the same tpnp— :

all water, a tremendous quantity of water must pass through the pile to get good = = .
pile of about 10 meters per second. = This means about 30 tons per second or 430,000 .~ ©

: 3 C ~ 4
* Cold; e S
. ‘V“\“.‘.' _-.' \
5%

ing such a tremendous quantity through ~ .  TVaterp
the necessary filters, etc., by recir- Sk e o s STk fl
culating the major sortion of the.water N ‘ i Sheoh

. through the pile and flowing only a e L e iz ol T e R S
small quantity of water through as T LT - o Make~ |
indicates that this make-up might .~ . T - &
amount to about 0.7 of a tam per = . "5 ) P | 5 b :
second for a 409 temperature ~«.~Reci tion Gener;.i t A

differential. The sketch at the: . = ., of Major Por- LN
right indicates this diagramatically. = '_‘1-'-'.:t,i.~0n. of Water Yater Tmf A

Mr. Cooper explained that it.is a frequent practice in industry where . o °
once through parallel flow would involve large quantities of watsr, to use gtage "t
gered baffles to produce a zigzag cross flow as indicated diagramatically. at the fRl
left below. lMr. Wigner suggested a cylindrical baffle at the periphery of the core = = ° -
as indicated in the two diagramatic alternates-at the center and right below. N

o ‘\
o

A . Baffle G5 s S
; e s T i ‘/’mund Core 1{? /\' sy o
l" : S e B s : : s
sy e 0 R O, P e i

Mr. Cooper enlarged upon the center sketch by suggesting a series of concentric
cylindrical baffles as a further refinement. The cylindrical baffles with the

“water entering at the center offer better utilization of the cooling stream than

the cross baffles since k is better in the . core than in the shell and half of the
power is produced in the core. The average power in the core per gram of metal is
about 10 times the average power for the shell. This means the core will produce
about 10,000 kw per ton of metal or about flve times the utilization at ¥, although
this figure is not far different from the expected utilization considered for P-9
piles. Since the shell metal will enrich in time, less metal will be required in
the center eventually. Although core poisoning will be a factor to consider, it

is probable that the metal activity rather than the poisoning will determine the
length of operation. » '
3 : N 2 "..1
. ”f ( £

S:ane tha removal o.t rods frmu such a pile does not. appear too ecsy,- LA
Mr. Young has suggested an arrangement B o oS SR ;
indicated diagramatically at the right
for overcoming this difficulty. In this
arrangement, the pile would be' mered
by a thick layer of water to act asa j 2
shield during the pulling of the rads e
and a reservoir for theyd.rculatmg et

‘xn’an, Mr. Vs'ednberé%’ félt_?r. e "
the scheme appeared relatively simple
and certainly much cheaper than s W _
type pile. Therefore, he felt it i
looked favorable and should be compmd xl.th aending Mr Urey's product t.o x o
Mr. Lawrence, ' . . bhoig i

' Eotr ‘\ ok “ 4% 2 4 ,v' )
¥ 3 ~;(...;-_ e S TR ’\‘qfl_ ~9,._---~.;-
9 R ,2‘."-“'.‘ > g s 07

i

; :_.';-r:g,,.@-:-; -

Mr. Vemon mdicated tlnt- the hatnea may have to be beryllium and. t.hat
there is another problem to consider,~-the vibrationof the rods at large velocities..
Mr. Wigner summed up the baffle situation as simply a compar:.son econamically and:
mechanically hetween uaing huge pumps with no baffles or accepting the baffle pm
blems with smaller pumps. He also observed thai the warping of the rods will be
no small problem. In answer to a question, Mr. Weinberg explained that the high
water velocity through the pile ise required for heat transfer and that the reason . =
. for the recirculating scheme was as follows. If the entire mass of water were eaet (s o
pumped through once, it would only be heated 1° or 29 which seems msteful By
recirculating, only a small amount of water would be ralsed about 40° uhile the
major portion of tho water would rema:!.n at the same tanperatm'e. ,

In answer to ¥r. Femi'a quest:.on a.bout transverse flow of cocling water, .
Mr. Cooper offered the opinion *pat it would probably introduce a greater pressure
drop than any other arrangement. - Mr, Vieinberg noted that they had alsc considered :
the scheme of letting local boiling eoccur near the rods,  but that, in this arrange-
ment, the heat transfer would be only half that at W. Mr. Vigner observed that a ek
perfunctory calculation indicated that the maximum heat transfer which could be
obtained by the boiling scheme would certainly not exceed that at W but that the
subject needed further study. Mr. Cooper said that there was mo question in a P-9
scheme that boiling was not the most efficient way of removing the heat but that in
a pile requiring such large volumes of water for removing the heat, boiling might
be more attractive. lr. Vigner suggested the arrangement in which boiling in the
liquid would occur at the surface of the rods with the bubbles leaving the rods
quickly and condensing in the balance of the cooler liquid. Mr. Young said that
the maximum heat transfer in a boiling scheme would only be about half that at .
Mr. Seitz pointed out that & boiling scheme enhances the corrosion problen.
Mr. Franck suggested using smaller pumps and no make-up water. In this case, the
water would be boiled off and recondensed, but Mr. Wigner said that Mr. Youmg's
calculations had indicated that this method would only get out about 1/3 of the
power and that thers was no great gain in adding a circulation system to a boiling
scheme. .

T M. ?d.gnor felt that for enrichments hi gher than 302, Mr. he.’mberg'a
-water pile was not so good but that for enriclments up to 30% it probably was .
better than Mr. Lawrence's isotope separation. Mr. Fermi felt there was a rguou-
ably good chance that 30% enriched material may become available and agreed wiw e
Mr. Wigxer that, accordingly, Jr. h‘einberg's scheme should be considered serimelr A
" In answer to a question regarding any additional problemsin thc
_ separation process, Mr. Cooper stated that the original plant at Clinton was dee i -
signed to operate on one week old material, although now operating on ten week old | ol
teria.l, and so this problem should not be critical in such a deeigx. ‘f"‘_ iy i
Mr. V.einberg pointed out t.hat the ordinary water pile origmally waa not :
very pracbtical but Mr. Szilard's suggestion makes it attractive again. ' :

Mr. Allison questioned. whether the fundamental point at fssue tainot.

‘will the 49 be as useful as 25 In the discussion following, the enriched o b1
water pile described above was oomparsd with My. Lawrence's electromagnetic ieotope
separation process. r. Lawrence uses Mr. Urey's metal which has been enriched =
from 0.7 to 0.9% of 25 and. carries it the rest of the way, but for every atom of .
25 put in by Mr. Urey, he gets out just one atom of 25. In the enriched ordinary :
water scheme, for every’ atom of 25 destroyed, we can expect l.) atoms of 49 to be _"
produced in the pile so thal the enrichment is used more eff:.cia:tly in thia type PRt
of procass than in the Lawrence schane. - Al . A : e 4% oSy

Because of the l:!mit,ed supply oi' material, Ur. Szilard felt that long- Ehriey
period operation was desirable although it was possible that the resonance aboorp-» ¥
tion by the fission products might poison the pile and stop the reaction. Mr. Wein- =
berg felt that when ooisom:l.ng stops ’che pile it is time to stog anyway for other o b
reasons. SRS AR =
’)C ke, S

Mr. Fermi reported that the supply of enric:.»d materi‘al for the oore o
would just be enough to keep one unit going. Hr. Szilar. then suggested leaving kA 2
the core in place and using the shell to obtain the 49, butl ir. Fermi pointed out . =
that the center material goec to 'oiecos soaner tlmm the shell material s Ly

Mr. Ohlinger made public Mr. Young's observation that considering tue
abundance of metal and difficulties in obtaining it, it would be very desirabls
to know what steps are being taken toward recovery of the large amount of material
which is now being lcst in the chemical process plant. Ir. Cooper reported that
work was being done on the recovery of uranium but that he had nothing definite
to report for possibly another month.

The next meeting will be on Friday, May 19th at which dr. Fermi will
speak. 8 . s

Jip