3,288,568 United States Patent Office Patented Nov. 29, 1966
1. 2 3,288,568 tion and extraction can be effected combinedly in one pro DIRECT DISSOLUTION OF WATER. INSOLUBLE cedure, and that stirring or agitation for dissolution and URANUM COMPOUNDS BY CONTACT WITH extraction is not necessarily continued, thus a simpler NEUTRAL, ORGANIC SOLVENTS PRETREATED apparatus suffices, are advantages of the method of the WITH NTRIC ACD invention. Ordinarily, when the water-insoluble nuclear Hiroshi Tomijima, Totsuka-ku, Yokohama, Kazushige fuel material is converted to a water-soluble compound or Tsukui, Tokyo, and Yoshimi Okoshi, Kawasaki-shi, a compound extractable with an extracting organic sol Japan, assignors to Tokyo Shibaura Electric Co., Ltd., vent, an excess amount of an acid is to be used, so that it Kawasaki-shi, Japan, a corporation of Japan causes a wasteful spending and needs apparatus and labor No Drawing. Filed Oct. 20, 1961, Ser. No. 146,447 10 Claims priority, application Japan, Nov. 18, 1960, for the recovery. According to the purifying method of 35/45,357 the invention, however, spending amount of the inorganic 9 Claims. (CI. 23-319) acid is limited to the theoretical amount, or an amount somewhat larger than that, for converting the material to This invention relates to the method for purifying nu 5 a compound extractable by the extracting solvent, thereby clear fuel materials. More particularly, it relates to a the amount of the inoganic acid required being smaller method for purifying nuclear fuel materials by contacting and the cost for recovering the acid being not needed. the same with a neutral organic solvent which has been Furthermore, purity of the nuclear fuel material is re treated with an inorganic acid. markably superior than that obtained according to the Among the purifying methods of nuclear fuel materials 20 conventional method, for example the one extracted by having heretofore been conducted, there are a method : an acidic organic phosphorus compound, e.g. di-2-ethyl in which an aqueous solution or solid of a water-soluble hexyl hydrogen phosphate. When extraction of a nuclear compound of these elements is extracted by an organic fuel material from a nuclear spent fuel having a higher solvent to yield the purified elements; a method in which radioactivity after being used for radiation in atomic pile a matrial containing these elements is mixed with an in is applied to the present method, a gentle solvent extrac organic acid, and the mixture is contacted with an organic tion is possible and cost of equipment is reduced. More solvent to extract these elements; and a method in which over, after decrement of the radio-activity to some extent, a solid containing nuclear fuel materials is contacted it is possible to allot the cooling time of the nuclear fuel with an acidic organic solvent, for example di-2-ethyl 30 to the time for extraction and extraction. In this case, hexyl hydrogen phosphate, without using inorganic acid physical form of the fuel is not important, and the meth in the prior step, thereby uranium being extracted from od can be directly applied to the metals, oxides, carbides, the solid. and their sintered products. An object of the invention is to provide a purifying Among the neutral organic solvent employed in the method of a water-insoluble compound of nuclear fuel 35 purifying method of the invention, there are neutral alkyl materials, such as various oxides, metals, carbides of phosphorus compound, such as trialkyl phosphate, dialkyl uranium, plutonium, and the like, and their molded arti alkylphosphonate, alkyl dialkylphosphinate, trialkylphos cles, which method does not involve a separate procedure phine oxide, ethers, esters, ketones, and the like. This of once converting the compound to a water-soluble com solvent may preferably be diluted to a required concen pound. Other objects will be apparent from the descrip 40 tration with a suitable water-insoluble organic diluent, tion which follows. such as kerosene, hexane, carbon tetrachloride, and the According to the present invention, thus, a method for like, according to the condition employed. This solvent purifying nuclear fuel materials is provided, in which a is shaken, prior to use for contact with the nuclear fuel water-insoluble nuclear fuel material is contacted with a material, with an inorganic acid, thereby involving the neutral organic solvent that includes an inorganic acid 45 inorganic acid in a complex compound form with the sol in a complex compound form with the solvent or in a vent or in a simple dissolved form. The content of the simple dissolved form through contact of the acid with inorganic acid in the solvent after the acid treatment is the solvent, thereby to separate from the impurities and adjusted according to the concentration of the neutral or to be extracted in the organic solvent. ganic solvent in the mixture of the same with the diluent, According to the purifying method of the present in 50 the concentration of the inorganic acid, and contacting vention, extracting ratio and degree of purification of the period of time. As to amount of the inorganic acid, nuclear fuel material to be extracted can be increased by powdered uranium oxide or yellow cake spends almost selection of a mixing ratio of a neutral organic solvent and theoretical amount of it, based upon the compound ex a diluent, content of an inorganic acid in the extracting 55 tracted into the extracting solvent, but pellets of uranium solvent volume of the extracting solvent used, extracting oxide or uranium carbide, or metallic uranium needs time, extracting temperature, size of the water-insoluble somewhat larger amount than the theoretical one. Nitric nuclear fuel material, and the kind of extracting neutral acid contents in the solvents, i.e. tributyl phosphate, di organic solvent. The facts that a specific step of convert butylbutylphosphonate, and methyl isobutyl ketone, in ing the water-insoluble nuclear fuel material to a water 60 cases of shaking the solvents with the same amount of soluble, or other, compound may be omitted, and dissolu nitric acid for five minutes, are shown in Table 1. 3,288,568
Table 1
Volume Concentra- Nitric acid Uranium percent of tion of nitric concentration concentration Neutral solvent Diluent neutral acid for in solvent in Solwent solvent in treatment after nitric after extracting of solvent, acid extraction, solvent Mil. treatment, Mil. Mi.
Tributyl phosphate Kerosene--- 30 5 0.85 0.442 y phoSp - 30 9 1.00 0.4935 Do. 50 5 1.30 0.7650 50 7 1.55 0.8700 100 5 1.88 0.9500 100 7 2.41 2300 30 5 0.99 0. 5460 30 7 1, 10 0.5995 50 5 1.47 0.7500 50 7 i. 66 0.860 - - - - - 100 5 2, 16 1. 0300 100 7 2.77 1. 3800 100 0.1 0.04 100 3 0.65 0.23 100 4 1.07 0.356 100 5 1. 40 0.47
Upon contact of water-insoluble solid nuclear fuel 25 2. Almost 80% of the uranium value in the material is material with an organic solvent thus containing inor extracted within 30 min. ganic acid, the solvent dissolves and extracts the nuclear fuel material. The rightmost column of the Table 1 shows Table 2 saturated concentration of uranium in the solvent in case Uranium concentration of extracting uranium from powdered uranium dioxide of 30 Extracting time (hr.): in solvent, M/l. 0.5u average particle size, which has been reduced by hy 0.5 0.35 drogen at 900 C. Thus, uranium is dissolved up to about %, in case of alkyl phosphorus compound, and about /3, in case of methyl isobutyl ketone, of mol concentration of nitric acid in the extracting solvent used. This may be 35 because substitution of solvates mainly serves for ex tracting action. Application of the present extraction is The extracting velocity is influenced by temperature. also possible with uranic concentrate as with powdered Especially when uranium is extracted from sintered urani uranium dioxide. In this case, a larger part of the im um dioxide, the effect of temperature is remarkable, thus, purities in uranium concentrate remains undissolved in 40 the extracting time being shortened by warming the uranium extracting solvent. Also, uranium can be direct solvent up to about 50° C. This fact is shown in the ly extracted and purified from solid moldings (shaped next example. articles) of uranium, for example sintered uranium EXAMPLE 2 dioxide, sintered uranium carbide, graphite-uranium diox ide press moldings, and metallic uranium, by use of the A 3 gram portion of fragments of sintered uranium neutral organic solvent treated with an inorganic acid. dioxide, which has been sintered at 1700 C. and has The solvent extracting the nuclear fuel materials out is density of 95%, is immersed into 55 ml. of tributyl phos filtered to remove undissolved residue of impurities, and phate/kerosene which has been treated with the same then scrubbed and stripped to yield an aqueous solution amount of 10 Normal nitric acid, to dissolve and extract of purified nuclear fuel materials. 50 uranium completely. As shown in the Table 3, the ex In extraction of nuclear fuel material from a water tracting time required is exceedingly shortened by warm insoluble solid nuclear fuel material by use of a neutral ing the solvent up to 50° C. organic solvent treated with an inorganic acid, uranium concentration in organic solvent increases with increase Table 3 of contacting time. Longer period of time is necessary 55 Uranium Yield of for complete dissolution in cases of sintered uranium temperature Extracting concentra uranium dioxide and sintered uranium carbide, when compared Extracting( C.) time (hr.) tion in sol (percent) with the cases of powdered uranium dioxide, uranic con vent (Mil.) centrate sintered graphite-uranium dioxide, and metallic 22- - 168 0.283 99.7
uranium. In any case of solid, the finer the degree of 60 pulverization or comminution is, the higher the extract 50. 15 0.283 99.9 ing Velocity is. Now, the present invention will more fully be described In extraction of nuclear fuel from water-insoluble with reference to the following examples, which are, how solid nuclear fuel material by use of a neutral organic ever, provided merely by way of illustration and not by solvent treated with an inorganic solvent, the yield de way of limitation. pends upon the volume of the solvent employed in the ex EXAMPLE 1. traction. This fact is shown in the next example. A 5 grams portion of a uranic concentrate containing EXAMPLE 3 about 80% of triuranium octoxide, which has been pull 70 A 5 grams portion of a uranic concentric containing verized up to about 200 mesh through, is shaken at the about 80% of triuranium octoxide, which has been ordinary temperature with a 35 ml. portion of 30% tri pulverized up to about 200 mesh through, is extracted at butyl phosphate/kerosene which has been treated with the room temperature by various solvents which have the same amount of 10 Normal nitric acid. The uranium been treated with the same amount of nitric acid, The concentration in the solvent increases, as shown in Table 75 results are set forth in Table 4.
3,288,568
Table 4
Wolume of Concentra- Uranium neutral Sol- tion of nitric Wolume of concentra Neutral solvent Diluent vent in ex- acid for the extracting. in extracting Yield of tracting Sol- treatment, Solvent, ml. tracting sol- uranium vent, per- MI1. went cent
30 5 35 0.390 90.7 30 5 45 0.326 95.6 30 7 32 0.420 86.0 30 7 40 0.367 98.5 50 5 20 0.660 92.5 50 5 22 0.650 99.0
Then, examples of extractions of uranium from graph- EXAMPLE 5 ite-uranium dioxide press moldings, uranium carbide moldings, and metallic uranium, by use of neutral or The following Table 6 sets forth the results of extrac ganic solvent treated with an inorganic acid. tion at room temperature of uranium from fragments 20 of sintered uranium carbide by use of neutral alkyl phos ------EXAMPLE 4 - - - - - ...... phorus compounds containing nitric acid which has been The following Table 5 sets forth the results of uranium treated in same way as preceding example.
Table 6 ------
Wolume of Concentra Weight of neutral Sol-tion of nitric Volume of sintered ura-Immersing Yield of Neutral solvent Diluent vent in ex acid for treat- extracting nium car- time uranium, vent,tracting percent. Sol- ment, MII. solvent, nil. bide g.pellet, percent
Tributylphosphate------Kerosine---- 50 10...'...... 15. 60 59 Do------dol- 70 0. 0 - i. 60. 68.2 Dibutylbutylphosphonate do. 50 0. 5. 1. 60 . . 58.8 Do------do------70 -10. , 10 ... 1. 60 58.8
extraction from pressed pellets of graphite-uranium . EXAMPLE 6 dioxide containing about 4.22% of uranium dioxide by use of tributyl phosphate treated with nitric acid of same The following Table 7 sets forth the results of extrac volumeat too high assolvent. temperature, If the the samples graphite have is whollynot been dispersed treated tionof metallic at room uranium temperature by use ofof uraniuma neutral from alkyl lathephosphorus scraps and settled in the solvent according to progress of dis- compound which has been treated in same way as preced solution and extraction of the uranium dioxide into the ing example. A larger part of the impurities in the metal solvent. The solvent after extraction of the uranium lic uranium is deposited in the uranium-extracting sol is filtered to separate from the graphite, the latter being vent as undissolved residue. Table 7 Wolume of Concentra Ete tion of Volume of . Weight of Immersing Yield of Neutra solvent Diluent REis nitric acid extracting metallic time, days uranium solvent for treat- Solvent, ml. uranium, g. percenty ment, Mil. Tributyl phosphate------Kerosene.--- 30 7 15 10 99.0 Do------do------50 0 0 3 99.5 washed several times with kerosene to remove the Then, uranium is directly extracted from a water-in uranium-containing solvent adhered thereon, while the soluble solid by use of an extracting solvent prepared by washings being combined with the filtered extracting sol- pretreatment of a neutral organic solvent with an inor vent mentioned above. The extracting solvent is 60 ganic acid, thereby containing the latter. The extract scrubbed and stripped to yield a purified uranium solu- ing solvent is scrubbed with a small amount of water or tion. - an inorganic acid, and thereafter uranium is stripped Table 5
Volume of Concentra tributyl tion of nitric Wolume of Weight of Yield of Neutral Solwent Diluent phosphate acid for treat- extracting Graphite- uranium, in extract- ment, Mil. solvent, ml. UO2 pellet, percent ing solvent, 9. percent
3,288,568 7 8 therefrom by use of pure water. To the resulting aque- 4. A method according to claim 3, wherein said com ous uranium solution is added ammonia to form pre- pound is contacted with said solvent at about 50 C. cipitate of ammonium diuranate, which, after separation, 5. A method according to claim 1, wherein said water washing and drying, is calcined in a quartz boat at 950 insoluble uranium containing compound is graphito C. in air to form triuranium octoxide. The following 5 uranium dioxide press moldings. Table 8 sets forth the impurities in the thus formed tri 6. A method according to claim 1, wherein said water uraniumployed in octoxide.the table areThe shown extracting in the solvents Table 9. 1 toThe 4 con-em insoluble uranium containing compound is uranium centration of nitric acid in Table 9 means that of treat- carbide. ing aqueous phase of same volume as solvent. l0 7. A method according to claim 1, wherein said water Table 8
Weight of No. of Wolume of Impurities in uranium (p.p.m.) uranium extracting extracting Uranium material material,3. solvent solvent,ml. 3 Cd Cr Cu Fe MI Mo Ni P Si Ag w
Uranic concentrate------5 1. 22 0.5 0.5 <12 1-6 10 >24 <0.5 <13 >200 >125 <0.2 <10 Do------5 2 40 0.25 <0.1 k12 55 12 1.5 <6 20 >25 <0.2
Table 9
Volumeneutral of tionConcentra of nitric No. of organic acid for extracting Seutral organic solvent Diluent solvent in treatment Solvent - extracting of extracting solvent, solvent, MII. Percent
------Dibutylbutylphosphonate.-- Rerosene---- 50 7
2- - - - Tributyl phosphate------do------30 7 3------do------do------50 10 4------do------do...----- 30 7 Next, an example is shown, wherein ether is em- insoluble uranium containing compound is metallic ployed as the neutral organic solvent. Tall. EXAMPLE 7 8. A method according to claim 1, wherein said neu - tral organic soluvent is selected from the group consist Into a 10 cc. portion of ethyl ether, which has been 40 ing of tributyl phosphate, dibutyl butylphosphonate, treated with the same volume of 5 Normal nitric acid, ethyl ether, methylisobutyl ketone and butyl acetate. is immersed uranium dioxide powder of 0.5u average 9. A method according to claim 1, wherein the organic particle size, which has been reduced by hydrogen at Solvent is mixed with a water-insoluble diluent. 900 C. The uranium is completely extracted into the ether at room temperautre after 90 min. 45 References Cited by the Examiner EXAMPLE 8 UNITED STATES PATENTS A 5 grams portion of uranic concentrate is immersed 2,869,980 1/1959 Grinstead ------23-14.5 into 40 ml. of 50% butyl acetate/kerosene, which has FOREIGN PATENTS been shaken with the same volume of 10 M/I. nitric 50 822,290 10/1959 Great Britain. acid,What uranium we claim is completely is: extracted. OTHER REFERENCES 1. A method of directly extracting uranium material AEC Document ORNL-2615, “Chemistry-Separa from a water-insoluble uranium-containing compound tion Processes for Plutonium and Uranium,' Jan. 5, without any preliminary dissolution thereof with acid 55 1959, page 5. which comprises treating a neutral organic solvent se- Bruce et al.: "Process Chemistry,” Series III, Pergamon lected from the group consisting of trialkyl phosphates, Press, 1959, pages 14-15. dialkyl alkylphosphonates, alkyl dialkylphosphonates, Bruce et al.: "Process Chemistry,” volume 3, Series III, trialkylphosphine oxides, ethers, esters and ketones with Pergamon Press, 1961, pages 188-195. nitric acid, contacting said compound with said treated 60 Clegg et al.: “Uranium Ore Processing,” Addison solvent whereby said uranium material is both separated Wesley Publishing Co., 1958, page 265. from impurities and extracted into said organic solvent. German application, 1,084,255, printed June 30, 1960. 2. A method according to claim 1, wherein said water- : insoluble uranium containing compound is a uranium ore L. DEWAYNE, RUTLEDGE, Primary Examiner. concentrate.3. A method according to claim , wherein said water- 65 CARLD. QUARFORTH, Examiner. insoluble uranium containing compound is a sintered L. A. SEBASTIAN, A. G. BOWEN, S. TRAUB, uranium dioxide. Assistant Examiners.