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THE FREPARATI’ONOF PLUTONIUM TRIClU4XW)E

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APPROVED FOR PUBLIC RELEASE


ABOUT THIS REPORT

This official electronic version was created by scanning the best available paper or microfiche copy of the original report at a 300 dpi resolution. Original color illustrations appear as black and white images. For additional information or comments, contact: Library Without Walls Project Los Alamos National Laboratory Research Library Los Alamos, NM 87544 Phone: (505)667-4448 E-mail: [email protected]

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ABSTRACT—-.

The following mthods for the preparation of plutonium tricbloride have

. been dmrelopod and their relative advantages and difficulties desoribed:

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.-

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Dehydration of?Pu(III) chloride solutions,

Hydrochlorination of p3utonium hydride,

Dc@dration of Pu(XV) chlorido solutions, followed by reduotion withhydrogen,

Eydrochlorimxtion of plutonium dioxide in the presence of ~drogen,

Eydrochlorination of plutonyl nitrato in the presonoe of hydrogen,

Chlorination of plutonium dioxide in the presenoe of oarbon tetra-chloride vapor,

HydrooNorination of plutonium(III) oxalate in the presence ofhydrogen.

The favored method at present is No. 7 which can be carried out relatively rapidly

on the present seal.eof operations (1-10 grams Pu) and.whioh appoara to offer the

least probability of giving trouble on

of the triohloride are i.ndicatod,such

bydroscopicity.

a 200-grm scale. Some of the properties

as the melting point, vapor preesure and

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THE PREPARATION OF PLUTONIUM TRICHLORIDE

Beoauee of the low tolerance limit for fluorine in plutonium for E-1,

the use of plutonium trifluoride or tetrafluoride in the preparation of plutonium*

metal has been considered undesirable. Consoquent2y,methods for the preparation

of plutonium trich.loridehave undergone int@n8ivo study by the “dry” chemistry

staff of Qroup C-5. Some of these findings have been reported very briefly in the

monthly progress reports of the Division of Chemistry and Metallurgy, but it se,enm

worthwhile to describe the various methods in greater detail.

First attempts to prepare PuCl~ involved dehydration of Pu(III) ohloride T

solutions in the presence of an~drous hydrogen ohloride and volatile substances

u6ed in tho reduction of the Pu(IV) to Pu(III). Consult Table I for the details

of the treatment involved. This proaoss appeare to result in reasonably pure.

PUC13,but it would probably be diffioult to execute on a 200.gram scale.

Good i%C13 nay be made by the action of hydrogen chloride on plutonium ‘

hydride (Table II). However, at present the hydride can be made only from the

metal, and thi6 proooss for preparing I%C1 would be feasible only if it we;?ede-3

eided to make

hydriding and

light element

metal first from the fluoride (or some other way). Sinoe the

hydrochlorination steps are expoctod to be inefficient for removing

impurities this plan seems to have little value.

Attempts to prepare PuC14 by dehydration of Pu(IV) chloride solution6,

followed by reduction of the PuC14 to PuC13 with hydrogen, have resulted in a.

nearly blaok~ water-insoluble produot of varying composition.

obtained in these 6tUdies (see Table III) it is not olear that

.

.,.

exists, but if it does it probably is unstable with respect to

●O* ● ●** ●** ●m.O. . . . * . .

From the results

anhydrous PuC14

dissociation into

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PuC13 and C12. Careful control of ~he rate of dehydration

the une of this process as nay be judged by the relatively

in

of

probably would permit

good ma%erial prsparod

run 89-58, but the generally discour~ging results have prompted the devolopmmt

better methods.

The relative difficulty of obtaining I%(III) and Pu(XV) ohloride 6olu-

tions after tho purification prooeduro ($ee LA-75 for a description of the proce-

dure in use up until recently),without the introduction of light element impuri-

ties, led to a study of the direot use of the PuO~(M03)2 solution EM it normally

Qame out of the purification sohenw in use. The prooedure found satisfactory on

a small male involved evaporation of the VISCOU8 Pu02(X03)2 solution to orptals,

an operation somewhit diffioult and slow to carry out on a 200==grcunseals beoause

of the he~lth hazard, ignition of the nitrate to PU02, and heating of the dioxide

in a istreamof approximately 50-mol percent H2, 50-rnolporoent HC1. Tables IV and

V present the results of these studies’. The use of”Pu02 ignited only to 350-400°

C has a definite advantage over that of highly-ignited dioxide as far aa apaed of

reaotion is ooncerned. On tho other hand, FW2(N03)2 apparently does not deaornpcme

quantitatively to Pu02 at these low temperatures, a fact which necessitates the

taking of’a small weighed aliquot for ignition at 1000° in order to determine the

percent conversion to chloride in the subsequent hydrochlorination. This genora2

method can certainly be made to work on a 200-gram 6cale, but thero is plenty of

evidence suggesting that the reaction is increasingly difficult to carry out in a

reasonable time as the scale goes up from 1 to 200 Rrams. The direct treatment of q●

Pu02(N03)2 with ~ + HCl, without conversion to dioxide first, appears to offer no

advantage over the use of fi02 (c%oeTable VI).



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Experiments on treating Pu02 with c12 + CC24, S2C12, eto., have not been

intensively pursued at Las Alamos owfig to the considerable effort being devoted

to this problem at Chicago. Some of the results

in the vapor pha8e, are presented in Table VII.

desirable from a purifioa,tionpoint of view this

obtained here, using C12 + CC14

Unless sublimation of PuC13 is

process has little to recommnd

5*, for it is difficult to get

tion of the PuC13.

The prooess which is

quantitative conversion without appreciable cublima-

..//

favored at this time consists of the partial drying

of a slurry of “~~(C204)309H2@’ in water by passage of air over the Blurry at

about 50°, followed by heating slcrwlyin a stream of fi2+ IiClfrom room temperature

to about 600°. Drying of the slurry proceeds rapidly because plutonium (111) oxa-

late is

ally at

oarried

very insoluble in water (IA-63) and, hence, the water present is substanti-

ita normal vapor pressure. On a gram =oala the hydrochlorination has linen

out extremely rapidly with suocess, but on a 5-10 gram scale it has been

found neoe8sary to carry out slowly the initial part of the hydrochlorination

(i.e., heating to about 250° chiefly to dehydrato the hydrated oxalate). In

general, there is Gtill a considerable saving of time over the best method formerly

in USO, and experiments suggest that a muoh greater rate of flow d the H2 + BCI

mixture, particularly during the early part of the hydrochlorination,

very rapid oonveraion to chloride. Slmdie8 made with relatively slow

are presented in Table VIII.

Use of the plutonium(lII) oxalate as a starting material in

will allow

rates of flow

the prepara-

tion of trichloride has the added advantage that tho oxalate precipitation fits

conveniently into tho ‘wett’purification prooedure, giving good separation of

uranium from the plutonium (whioh the rest of the “wett’procedure does not) and

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of giving additional purification from light elements. The extra

to convert the PU02(N03)2 to the OXalate (by 31

tion of H2C204) is only of the order of two hours, so the not

the older dioxide process of making the triohloride is of the

considerable amount of work remains to be done in engineering

gram scale.

In general, the preparations tabulated were oarried

reduction and adcii-

sav~ng in time ov6r

order of a day. A

the prOCeS8 on a 2C0-

out using plat’inum

or poroelai.ncontainers placed in a quartz tube electrically heated and through

which the desired gas oould be passed. Temperatures were

alumel therinooouples. The yields were ger.erallyfollowed

which were cheoked from time to time by chemical analysis

and by X-ray analysis (Group C-8).

measured with chromol-

by aareful weighing8

for chlorine (Group C-9)

Several attempts have bcxm made to sublimo PuC13 in a high vacuum be-

cause of the possible use in freeing the trichloride from traces of dioxide or

oxychloride. These experiments have demonstrated that PuC13 can be sublimed in :1

vacuum, compact blue-groan crystals being obtained in contrast to the very finoi

granules normally obtained h the “dry” preparations from oxide or oxalate. The

exact optimum conditions for obtaining highly pure triohloride have not been as-

certained as yet.

Pure plutonium trichloride appears to be a blue-green substance, melting

at about 760° C, with a vapor pressure (as measured by moleoular effusion) of

approximately 5 x 10-6 mm Hg at 600°, 3 x 10-4 mm at 700° and 2 x 10-3 mm at 750°. .

The vapor pressure values are probably not sufficiently accurate to allow oalaula-

tion of a reliable value of the heat of sublimation. The triohloride is somwtihat

hydroscopic, slowly hydrating in air (R.IL= 30-40 percent) to form what appears

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8everal hours at 250°. The triohloride is oonvertetito di-

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UNCLASSIFIED - Federation of American Scientists APPROVED FOR PUBLIC RELEASE APPROVED FOR PUBLIC RELEASE This official electronic version was created by scanning the best avail able