Purification of uranium oxide

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Title:
Purification of uranium oxide
Series Title:
United States. Atomic Energy Commission. MDDC ;
Physical Description:
4 p. : ; 27 cm.
Language:
English
Creator:
Hoffman, James I
U.S. Atomic Energy Commission
Publisher:
Atomic Energy Commission
Place of Publication:
Oak Ridge, Tenn
Publication Date:

Subjects

Subjects / Keywords:
Uranium   ( lcsh )
Uranium oxides   ( lcsh )
Uranium -- Purification   ( lcsh )
Solution (Chemistry)   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Bibliography: p. 4.
Restriction:
"Date Declassified: March 18, 1947"
Statement of Responsibility:
by James I. Hoffman.
General Note:
Manhattan District Declassified Code
General Note:
"Date of Manuscript: Unknown"

Record Information

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University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 005024351
oclc - 288524543
System ID:
AA00009285:00001


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MDDC 777


UNITED STATES ATOMIC ENERGY COMMISSION









PURIFICATION OF URANIUM OXIDE



by
James I. Hoffman


This document consists of 4 pages.
Date of Manuscript: Unknown
Date Declassified: March 18, 1947


This document is issued for official use.
Its issuance does not constitute authority
to declassify copies or versions of the
same or similar content and title
and by the same authorss.





Technical Information Division, Oak Ridge Directed Operations
Oak Ridge, Tennessee


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PURIFICATION OF URANIUM OXIDE


By James L Hoffman


INTRODUCTION
In the early summer of 1941, Leo Szilard, (member of Power Production Subsection of the
Uranium Committee), gave a sample of impure uranyl nitrate to the author and requested the the
uranium be separated from everything else.' It was his desire to obtain the residue, after the re-
moral of uranium, for measurements of neutron absorption. During the same period, samples of
impure uranium oxide were sent to the Bureau of Standards for chemical analysis. For both purposes
it was desirable to use some solvent that would dissolve the bulk of the uranium without dissolving
any of the other substances. The solubility of uranyl nitrate in ethyl ether, first reported by
E. Peligot,2 suggested its use for extraction of uranium as the nitrate, somewhat as ether is used in
steel analysis for mte extraction of ferric chloride. This extraction had been successfully applied in
19.19 for separating uranyl nitrate from rhenium and certain rare earths in work on the determi-
natio-, of rhenium and molybdenum,3 but, because of the conflicting statements concerning the sol-
ubiliry of the rare earth nitrates in ether,4 it was obvious that experimental work was necessary,
espeLally since Szilard stated that certain members of the rare earth group are strong neutron
absorbed r .

The work herein described is not intended to give the procedure finally used in large-scale pro-
duction of uranium nor the methods used in the various laboratories of the Manhattan Area. Many
improvements in procedure have be. made since this preliminary work was done.

A procedure is given for the purification of uranium oxide by converting the oxide to the nitrate
and partitioning the nitrate between a large amount of ether and a relatively small amount of water.
In modified form, the procedure was found to be applicable to pitchblende and carnotite ore concen-
trates.

EXPERIMENTAL WORK
The bulk of the uranium was extracted with ether from 1.00 g of uranyl nitrate, UQ(NO,)2.6HO,
to which had been added 5 ml of water and "rare earth" nitrates (equivalent to 0.0084 g of oxides)
containing cerium, praseodymium, neodymium, erbium, gadolinium, terbium, dysprosium, holmium,
erbium, ytterbium, lutecium, scandium, yttrium, lanthanum, and thorium. After removal of most of
the uranium, the combined "rare earths"were determined in the residual water solution by precipi-
tating them as fluorides, converting the fluorides to sulfates, then precipitating as oxalates, and
igniting the oxalates to "'rare earth" oxides. The oxides weighed 0.0086 g. In this particular case
the uranium extracted by the ether was not examined for impurities, but it was evident that extraction
of uranyl nitrate with ether should be a good starting point for the purification of uranium.

To obtain a quick answer to the possibility of using ether for the purification of uranium, the
elements listed in mixture A' in nitric acid solution were evaporated as far as possible on the steam

Mixture A consisted of 2.5 g of uranium metal dissolved in an excess of nitric acid. To this was
added as nitrates 2.5 mg each of copper, antimony, lead, aluminum, lithium, zirconium, indium, gal-
lium, bismuth, potassium, dysprosium, cadmium, gadolinium, chromium, magnesium, holmium,
cobalt, tin, calcium, and 10 mg of a mixture of 'rare earths" known to contain cerium, lanthanum,
scandium, praseodymium, thorium, and yttrium.
MDDC 777 [ 1















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bath. The residue was extracted with 100 ml of ether, the ether was washed twice with 5 drops of
water, and then the uranium in the ether was converted to oxide.

Qualitative spectrochemical analysis showed that this oxide contained only calcium, magnesium,
and silicon, besides uranium. These encouraging results prompted further experiments which
formed the basis for the procedure given herewith.

PROCEDURE USED FOR THE PURIFICATION OF URANIUM OXIDE

Fill, grams of UO, wj tir -n.-ferred to a 600-mi beaker, 75 ml of diluted nitric acid (1 volume of
concenti ted nitric acid sp gr 1.42 diluted with 1 volume of water) was added, and the beaker was
idc :d .n the -teambath until all action ceased. The insoluble matter was removed by filtration, and
the resadue uas washed 4 or 5 times with diluted nitric acid (I volume of nitric acid, sp gr 1.42.
diluted with 20 volumes of water). The filtrate and washings containing the uranyl nitrate were evap-
orated to drynes- on the steambath. To the cooled and dried residue in the beaker, 5 ml of water and
100 ml of ethyl ether were added, and the beaker was swirled until the uranyl nitrate was dissolved.
T..e large quantities of Lmpurities caused the aqueous phase in the bottom of the beaker to have the
appearance of an emulsion, but this did not interfere in the separation because it was possible to
pour the ether into a separatory funnel without mixing with the water layer.

The ether was transferred to a separatory funnel, the beaker was washed 3 times with 5-ml
portions or ether which were likewise transferred to the separatory funnel. The funnel was stoppered
and -haken vigorously for 1 2 to 1 minute. After allowing the liquid to stand 3 minutes, a few drops
of water appeared in the bottom of the separatory funnel. This water was drained into the beaker
which originally contained the ether solution. Five ml of water was now added to the solution in the
separatory funnel, the mixture was shaken vigorously, and the solution was again allowed to stand
until ito layers formed. The aqueous phase was drained into the beaker which originally contained
the ether solutionn The washing with another 5-mi portion of water was repeated once more.

To convert the purified uranyl nitrate to oxide, a little water was added to the ether, the ether
was cautiously evaporated, and the residue was ignited to UO, at 1000 4C. It was afterward found
preferable to add 20 ml of water to the ether solution, shake vigorously for one minute, and allow the
liquid to separate into 2 layers. The water layer was drained into a suitable dish, and the extraction
with 20-mi portions of water was repeated until the ether above the water was colorless. Three or
four .uch extractions were sufficient to remove the uranium. 'he combined water extracts were
evaporated to dryness, and the uranyl nitrate in the residue was ignited to UO at 1000"C. The ether
from which the uranyl nitrate had been removed was suitable for future extractions.

The procedure was also applied to the extraction of uranium from pitchblende and carnotite ore
concentrate; by digesting the ore concentrate with nitric acid, evaporating to dryness, and extracting
the residue with ether. The efficacy of this method of purification is shown in Table 1. The table
shows that in many cases impurities that were not detected in the original oxide were concentrated and
detected in the water extract. Note especially Ce, Co, Cr, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sc,
Sm, Tb, Tm, anrd Y.

DISCUSSION

It was evident that the purification of crude uranium oxide and the removal of uranium from ore
concentrate by conversion of the uranium to uranyl nitrate and extraction with ether had possibil-
ities because practically all impurities were removed in a single operation. Tests by L. F. Curtiss
(Chief of Section on Radioactivity at the National Bureau of Standardsl indicated that practically none
of the radium in the original ore was extracted by the ether.

Under stress of wartime conditions not all the possible confirmatory tests were made, but, as a
check on removal of the rare earths, the purified oxides obtained from No. 155 and No. 181, Table 1,
were put through a second purification by the same procedure. The water extracts in this case
showed no rare earths. Tests by K. D. Fleischer indicated that if 0.5 mg of "rare earth" oxides had


















MDDC ?77

Table I Spectrocnemlcal Analysis* of products obtained in the purification of uranium oxide or
recovery ol uranium from are LonccilrJLes



ELle UO4. N 155 Lq No. l d C .rtulale ore Pllchbicrde ore
mrnl concertrale concentrale


Original Witer Pirtiied
oxidE e -irac. oxide


Origlnil Water Purdifed Or'inad lre U,O ob Original ore U0,
oxide ctra;rt oxide concentrate i ained concentrate obtained


Ag T v T
Al VW T VW
As ; M
An 7
B T VW
Ba -
Be
BI VW W

Ca VS --
Cb
Cd
Ca -
C -

C
Cr 1 %1 r
D,
Er M -
Eu I M
Fe 0 .1 VW

o M
e -u M -
Ge
HI
Hg
Ho
In
Ir
K T -T
Li T
L T
Lu '
Mig I Tr








P r, I w
Mr, *'. l -
Ml. A M W

Pr 9-







PI -
Ra
PDo
Re
Rn
Ru

cL -
. M M VW
im -


Ta
r, -i
5r

Ta -


T -
T'
Tn


Tr, -
U VS Vi VS
V >W 0 -

Y -
Yio M


Vvk W I
VW W VW
Vw w vw
W W
VW VW -
T W -
- VS







W
W M -
- vs -


W M T
S
M

W M VW

M


M
VW

M
T
VW
VW
W VW
W
M
S T
W
W


M

W
W






M
W
W W
W
-) -











VW
vw


W
l a VS VS
VS

VS
M


S M


M T M
W .
S VW
VWS


VW W

VW
vW





S


vs
vs
w
VS
W

M


Tne a :ic-nation i a ind S crre :pona to major consliluer.r t(realer tian I per cnl., M ana W
to mzaor conSliluenrr It to ] 01 per cent): and VW r ann FT to Irarc cc-r ntlluentlr les- Lhan 0.01
per ceat). TnE io3.:cre of a do ignaiion lnmic.3iie: tIrl i tel a: not maoi. ior thaI element

SBy B. F icriDrlr ina H R MulIn.
I Tha WilEr -xtra-iU conairnea rare eartni. but no attempt w'a mjde to ioenUly therm iividudlly.


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4 MDDC 777

remained in the purified oxide, a positive test would have been obtained here. This showed that by
this simple procedure the combined "rare earths" in the purified oxide were reduced to less than
5 parts per million. The spectrochemical tests showed that not more than 0.5 part of cadmium or
boron per million remained in the purified material.

SUMMARY

A procedure is given for the purification of uranium oxide by converting the oxide to the nitrate
and partitioning the nitrate between a large amount of ether and a relatively small amount of water.
In modified form, the procedure was found to be applicable to pitchblende and carnotite ore concen-
trates.

REFERENCES
1. Smyth, Henry D., Atomic Energy, Princeton University Press, 1945.
2. Ann. Chim. Phys. (3) 5:5 (1842).
3. Hoffman, James I. and G. E. F. Lundell, J. Research NBS 23: 497 (1939). RP1248.
4. Wells, R. C., Wash. Acad. Sci. 20: 146 (1930); Soddy, F. and R. Pirret. Phil. Mag. (6) 20: 345
119101: Hillebrand, W. F., U. S. Geol. Survey Bull. 78: 47 (1891); Davis, C. W.. Am. J. Sci. (5)
11: 20 (1926).










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