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United States Patent (19) 11 Patent Number: 4,832,924 Tomoshige Et Al

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United States Patent (19) 11 Patent Number: 4,832,924 Tomoshige Et Al United States Patent (19) 11 Patent Number: 4,832,924 Tomoshige et al. (45) Date of Patent: May 23, 1989 54 PROCESS FOR PRODUCING URANIUM 4,292,279 9/1981 Reusser ................................. 423/15 4,375,452 3/1983 Jan et al. ................................. 423/7 OXIDES 4,517,096 5/1985 Sekine et al. ... 210/668 75) Inventors: Shozo Tomoshige; Hideto Obara; 4,696,768 9/1987 Ali et al. ............................. 42.3/7 X Kozo Kondo, all of Uji; Keiichiro Otomura, Kurayoshi; Soichiro Yano, Primary Examiner-John F. Terapane Okayama, all of Japan Assistant Examiner-Virginia B. Caress Attorney, Agent, or Firm-Wenderoth, Lind & Ponack 73) Assignee: Doryokuro Kakunenryo Kaihatsu Jigyodan, Tokyo, Japan 57 ABSTRACT The present invention provides a process for producing (21) Appl. No.: 127,913 a uranium oxide by dissolving a yellow cake in sulfuric 22 Filed: Dec. 2, 1987 acid or hydrochloric acid, bringing the obtained solu (30) Foreign Application Priority Data tion into contact with a chelating resin of diaminocar boxylic acid type and subjecting the product to neutral Dec. 26, 1986 JP Japan ................................ 61-3102 izing precipitation followed by heat treatment. By the 51 Int. Cl. .................... C01G 43/01; CO1G 43/025; contact of the solution with the chelating resin, iron, C22B 60/02 copper, molybdenum and Vanadium among the metallic 52 U.S. Cl. ........................................ 423/7; 423/260; impurities are removed and in the subsequent neutraliz 423/15 ing precipitation step, other metallic impurities such as 58) Field of Search ........................ 423/260, 7, 11, 15 aluminum, calcium, magnesium, sodium and potassium are removed. This process can easily produce uranium 56 References Cited oxide having a high purity using a simple apparatus. U.S. PATENT DOCUMENTS 3,052,515 9/1962 Donaruma .............................. 423/7 7 Claims, No Drawings 4,832,924 1. 2 flammable solvent is used so that an explosion-proof PROCESS FOR PRODUCING URANIUM OXDES apparatus is not required. After intensive investigations made for the purpose of BACKGROUND OF THE INVENTION accomplishing the above-mentioned objects, the inven The present invention relates to a process for effi tors have found that iron, copper, molybdenum and ciently producing uranium oxides, and more particu vanadium among the metallic impurities can be effi larly, to a process for effectively removing metallic ciently removed by dissolving the yellow cake contain impurities contained in a starting material of a yellow ing the metallic impurities in hydrochloric acid or sulfu cake to produce uranium oxides with a high purity. ric acid in place of nitric acid and then bringing the The term "yellow cake' used herein means a uranium 10 resulting solution into contact with a chelating resin of oxide concentrate that results from milling uranium ore. diaminocarboxylic acid type, and then the other metal It typically contains about 80 to 90% U3O8. lic impurities such as aluminum, calcium, magnesium Various processes for refining uranium have been and the like can be removed in the subsequent neutral proposed. Among them, a process wherein a uranium ization step. The present invention has been completed oxide is produced as an intermediate is employed 15 on the basis of this finding. widely in many countries. When a yellow cake used as According to the present invention, there is provided a starting material in this process contains metallic im a process for producing uranium oxide from a yellow purities such as iron, copper, molybdenum, vanadium, cake, which comprises dissolving a yellow cake in an aluminum, calcium, magnesium, sodium, potassium and acid selected from the group consisting of sulfuric acid the like, the purity of the resulting uranium oxide or and hydrochloric acid to form a solution, bringing said uranium hexafluoride obtained by further refining solution into contact with a chelating resin of diamino thereof is reduced. Therefore, these metallic impurities carboxylic acid type, subjecting the thus treated solu must be removed, tion to neutralizing precipitation by adding ammonia These metallic impurities have conventionally been into the solution to precipitate ammonium diuranate, removed by solvent extraction in a tributyl phosphate/- 25 and heating the thus formed ammonium diuranate to nitric acid system. In this process, the yellow cake con form uranium oxide. taining the impurities is dissolved in nitric acid and then The yellow cake employed as a starting material in the impurities are removed by extraction with tributyl the present invention usually contains therein, in addi tion to uranium, metallic impurities such as iron, cop phosphate (TBP), solvent. Then a solution of uranyl 30 nitrate UO2(NO3)2 thus obtained is concentrated by per, Vanadium, molybdenum, sodium, aluminum, cal evaporation to precipitate uranyl nitrate hydrate (UNH cium, potassium, magnesium and the like. By the treat process) or, alternatively, ammonia is added to the ura ment of the solution of yellow cake with the chelating nyl nitrate solution to crystallize ammonium diuranate resin the metallic impurities of iron, copper, molybde (NH4)2U2O7.2H2O (ADU process). The uranyl nitrate 35 num and vanadium are removed. The remaining metal hydrate (UNH) or ammonium diuranate (ADU) is ther lic impurities which have not been removed by the mally decomposed by roasting it at a temperature of treatment with the chelating resin are removed in the 500 C. or higher to form uranium oxide and to recover subsequent neutralizing precipitation step. nitric acid or ammonia. Ammonium diuranate formed in the neutralizing pre The above-mentioned solvent extraction process is cipitation step is heated to a temperature of 350 to 550 not preferred from the viewpoint of environmental C. to form uranium trioxide. When ammonium diura pollution, since a waste liquor containing nitrogen and nate is heated to a temperature of 550 C. or above, phosphorus is formed in a large amount because nitric triuranium octoxide is formed. acid and tributyl phosphate are used. Further, the mate DETAILED DESCRIPTION OF THE rials forming apparatus employed in the process are 45 INVENTION limited, since nitric acid is used. In addition, this process As described hereinabove, the chelating resins of is economically disadvantageous, since the solvent ex diaminocarboxylic acid type used in the present inven traction is conducted in multiple steps with a mixer-set tion are capable of effectively removing iron, copper, tler and, therefore, a large apparatus and a large area for molybdenum and vanadium in the solution of the yel the installation thereof are required. Another problem is 50 low cake in sulfuric acid or hydrochloric acid. Exam that an explosion-proof apparatus is necessitated, since ples of the chelating resins of diaminocarboxylic acid the solvent is easily inflammable. type capable of selectively removing iron, copper, mo SUMMARY OF THE INVENTION lybdenum and vanadium from the yellow cake solution It is therefore a primary object of the present inven 55 include chelating resins prepared by crosslinking a phe tion to provide a process capable of producing uranium nolic compound of the following general formula: oxide having a high purity by removing the above-men tioned metallic impurities from the starting material of OH yellow cake. It is another object of the invention to provide a 60 (CH2COOM)2NCH2 CHNCHCOOH)2 process for producing uranium oxide wherein solvent extraction using nitric acid and tributyl phosphate is not R R2 employed so that no waste liquor containing nitrogen and phosphate is formed, and no large production unit (wherein M represents an alkali metal or hydrogen, and such as a mixer-settler or large area for the installation 65 R1 and R2 each represent hydrogen or an alkyl group thereof are required. having 1 to 3 carbon atoms) with phenols and aldehydes It is a further object of the invention to provide a to form a three-dimensional structure. As for these che process for producing uranium oxide wherein no in lating resins, those capable of reducing the iron concen 4,832,924 3 4. tration of an acidic electrogalvanizing bath are known can be precipitated, filtered and washed easily. In this from Japanese patent laid-open specification No. neutralizing precipitation step, only ammonium diura 54-121241 (laid-open on Sept. 20, 1979) and particularly nate is precipitated, leaving aluminum, calcium, magne that known under the trade name Uniselec UR-50 (a sium, sodium, potassium and the like contained as the registered trademark, a product of Unitika Ltd.) is suit 5 metallic impurities in the supernatant liquid. ably used. The resulting ammonium diuranate precipitate is sep The solution of the starting yellow cake contains arated from the supernatant liquid and then heated or uranium and at least one of the above-mentioned metal calcinated at 350 to 550° C. to form uranium trioxide or lic impurities such as iron, copper, molybdenum, vana at 550 C. or above to form triuranium octoxide. These dium, sodium, aluminum, calcium, potassium or magne O uranium oxides can be reduced to form uranium diox sium. The content of the metallic impurities in the yel ide, which can be treated with hydrogen fluoride to low cake is not particularly limited. form uranium tetrafluoride and further uranium hexa In the treatment of the yellow cake solution with the fluoride. The uranium oxide produced by the process of chelating resin of diaminocarboxylic acid type, it is the present invention is usable as a yellow cake having preferred to adjust the pH of the solution to 0.5 to 2.5. 15 a high purity. This product can be used as a starting When the pH exceeds 2.5, uranium in the yellow cake material (yellow cake) in a conversion process for pro solution begins to be precipitated to cause a loss thereof ducing uranium hexafluoride from a yellow cake of a and unfavorably form a radioactive waste. On the con high purity such as a dry process employed by Allied trary, when the pH is lower than 0.5, iron, copper, Chemical Corp.
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