Impregnation of Graphite w. Uranium Compounds for Fuel Rod Mtls [declassified

35 Pages·1948·2.197 MB·English

I
Photosta~~ t Ch for . . .,- .~ .. . ., ..-- - - I_
i
I,
Access Perm
Available from
Operated by the tbiversi%yo f Chicaa
mdex
\
DISCLAIMER

This report was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor any agency Thereof, nor any of their employees,
makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial product,
process, or service by trade name, trademark, manufacturer, or
otherwise does not necessarily constitute or imply its endorsement,
recommendation, or favoring by the United States Government or any
agency thereof. The views and opinions of authors expressed herein
do not necessarily state or reflect those of the United States
Government or any agency thereof.
DISCLAIMER

Portions of this document may be illegible in
electronic image products. Images are produced
from the best available original document.
'0
_-
9
8
I
-T?
:1'9
19
1'6
?E
.
22
2€
2€
d'd'
. a
I '
,'. .
!' I
.'
....................... ............. . .
..... . . . . . . . . . . . . .
. . . .
. . . . . .. . . . . . . . . . . .
00 "0- 2 OPO 00 ,0 c ; 0 t. o o e 0 0 e ?
Table
I. Comparison of the Urdm Conte!nt Attainable by Impregnation of
Various Graphites by the Evacuation and Refluxing Techniques 12
o(iooooo
. I*
I1 Variation of u8.anfum Content Observed in the hprsf7ilation of the
--7 ' Different "yp3 of GTaphite 13
O O O O O O o O O O O O O ~ O . o O o e o o ~ o ~ o o ~ o o o ~ ~ ~ ~ ~ ~ o ~ ~
\l
4..I. ) - I11 Effect of T i m of Rgflwdng on Uranium Content of SpIarndapd Graphite
S ~ P ~ S S 3.6
oooooooo~oooooooooooooooaoooooooooooooooooooaoooo~o~eoaoooeo
VI Effect of Repateti hpmgnations by the Elvacuatfon Technique an the
Uranim Content of Graphite Samples 20
O O O O O O O O O O o ~ O e O O O O a O o o o o ~ ~ ~ ~ ~ ~ ~ ~
VI11 Impregnatton of Graph%%@by Immersion in a &xrme Solution of
uranyl Nitrate 21
I . ~ o ~ b ~ o a o ~ ~ ~ ~ o ~ ~ o ~ ~ o ~ ~ o a o o o o o o o o o o a o o o o o o o a u o o o o o o o o o o
, 7 IX Cornparism of %he,E ffic5.enc-y of hprqpation of AGOT-E GrapMtcs
"+$'2 by bflwdry in a Solution of Uranyl Nitrate 3.n Various Solvents ooo 22
d'
X Effect of Dryins and Firing Ppocedum on the Distributiion of
Dpaplium ia aP@ih SEllQh8 oooooooooooeQaoobaoooooeooooooo9oooooeoo 26
X I Eff& of Nitric &id Pretreatment of AGR Waphib on the IiespruaP,an%
Water Absorpt5.m 29
0 0 0 0 0 0 0 0 0 o O . o o . . O O o O o o o o ~ ~ o o ~ o ~ o o o o o o ~ ~ 6 e ~ o o ~ O o o o o ~
I
' i
. f,
'I
1 :;-.,j ? I
i I 1 I 1
i: ;:i i ............ ......1 ., ........................... .
. . . . . . . . ..!.! . .; . . . . . . .
I J
. . e O D 0 0 0 0 0 0 0 0 0 c o
00 OOP 2 :cc 3 : ;; r: ~ . . .
$ -
el.
- -
e=.
2 20s
1! : L; $p
.................. .... ..:!- ...i..... .............
. . . . . :.: ..j. ".,':
. . . . . . . . . . . . .: . .: .:
:* :*
< I -
00 000 0 COP E 30 E? " 'I
eruch.mterial WBS espcidly susceptible %o thmnaJ. cr.ackup, dm to the law
resistance of fabsicated berylU %o %hemal stresses, This thermal cracking
of such fuel %&e8 woulil probably be the lfmsting factor Sn operating the
pile at high erisrgy levels (maker than 4000 k ~ )The,~ us e of graphite was
therefore suggested as a replacmen%f or bewllia in the fuel rod becauses of
its plasticity 24% high t q r e t w s , its mcharnical strm&hg its repbtively
~ U WCO S% and I t s a~ailalbilfty, Also it r~eermotd likdy that the C M pCro- ~
cessing of spat fuel m& would be eayiep when made of graphite rather thzm
beryllls, Furthemre, a great deaf of mcperimce had been dbtained with
maphite as a pile mtep.ihillo" ) The pmgram described hrein mas undertaken
to develop a method for incorporating uranium 5nto a graphite he1 rodo
Two approaches to the pblem were suggestede (I) that uranium oxide
be mixed with coke flour ayrd the mixture graphitized, and (2) that the uranium
be incorporated Snto tbe fgbrieated graphilx radso Since no high temperature
facizities were available for graphitization at this labmatory, attention
was focusled on the secmd approach," The &gome M a t i d Laboratory has,
*
A prelasarg a c p e m %w as carried out at the Apsanng Naticmal
Laboratory before abandoning the first approach, Pawtiered graphite wae added
to a solution of mmy3 nitrab hex&ydrate and the xnlxtm was evaporated te
a thick paste. This waa packed into a beryl-lia tube and baked over nighti arP,
4oo°C, whereby the remai- water was remmed and the nitrate decomposedo The
temperature of the ova was then raiseid to P4SOoC and held there fop-a fem haurs,
When the ample! waa removed from the furnace it waa found to be in the form d
- a ffne powder and it waa obvPaw that to produce coherent material, it would
be necessary to mix the powders in -p%tch and actually regraphitize at very n-tigfi
temratures 5 --
Sfice graphite is quite porous, it %vim belimed that the pores could
be filled with a solution of a uranium salt which could then be changed %o
a form stable under pile conditions, Uranglnitrate was the salt chosen
because it has a high solubility and is easily converted to an oxide stable
at the proposed pile tmp@ratums, Early eatbates of the amount of uranium
in the Danielse pile showed that approximately Oo04 g of U3O8 ( m i c h d
h the 238 isotope) per cubfc centimeter of graphite would be requirsdo( 11
-
On a weigh% basis, the fuel elemtrs would have to ham 2 3%U S O ~d~e mding
on the density of the graphite, Hmee the prfmary recprhmntt of the process
-
WWI that it should produce fuel roder contafning 2 3% U808@ vsferably by
one fmprognation, w5th a8 littb vnriation in uranium content a~ w a p~o ssibh.
The process selection was also guided by the fact that the uranium lehuld be
' >
depOsi%ed UIlifOxdy tb*out th@ fuel element,
This report describes a process for making -1rods by impregnatim
with uranyl and gives a swnnapg of %he experir&entawl ork Xeading to
,- this pPoCesl30
Three % m ao f graphlee, aU. products of the National Capban Company,
..
.- .-
. ,
..-
......................
. . . . . . . . . . . . . . . .
.. ............... .. ...............
__
0 0 0 e 0 0 . ?"-e _.0 0 0 e o D O
~
On the basis of the reproducibility of its properties, type L1508-A
seem to be the best graphite for fuel rod material of the three types
tested,
The process itself consists of five steps:
(3.) Fabrication of a fuel rod blank from graphite stock
. --.
I
-L (2 ) Pretreatment
(3) Impregnation
(4) Dryfrs
(5) Conversion to a stable urmiun compound
2,2 Fabrication of the eD8.cr_r;nit;s
Design requirements for the fuel rods called for a hollow cylinder, 6
inches in lengtho 1,500 inches OD and 0,875 inches ID, The large graphite
bars were cut into s d blo cks slighLly larger than the outside &bensions
of the fuel rods. They mere then cut d m o n a la.the to the outer diameter
and the inner dimension was obtained by drilling and reaming,
2,3 Pretreatmen%
The graphite, Puel pods were boiled. in rater for 30 minutes to remove
loose graphite pander remaining from the machinbg operations. They were
them fired in helium at 80O0C for 30 m3nutes tlo water and any volatile
perptulve
substances present. About O,l$ by weight of the graphite vras burned off in
this step since no effort was made t o pur* the helium,
2,4 Impregnation
The fuel rod was’pPaced jlrm a vessel which was subsequently evacuated,
The *peosure miis maintained below 1 mm of mercury for about 10 minutes, follacsing
_.
which an aqueous soltrtim of u~leayrlnitrate~ rma dmi4;tad t;O the vesseZ to cover
96.2 208
....... ....................
. . . . . . . . . . . .
.. ............. .. ............... ..
0--0 0 0 0 -0 - ,=0 0- ’-0 0 0 0 0 0 O D
~