Determination of Trace Quantities of Fission Products in Nonirradiated Natural and Depleted Uranium Salts

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Abstract
The occurrence of a number of fission products in pitchblende and in nonirradiated natural and depleted U salts with 10-4 dis/sec/g-U, was recently reported by Kuroda and co-workers. The following nuclides were detected: Sr89, 90, 91, 92, Mo99, I131, 132, 133, 134, 135, and Ba140. These fission products are formed predominantly by the spontaneous fission of U238, and it is possible to obtain the general shape of the mass-yield curve for the spontaneous fission of U238 from the equilibrium activities of the fission products found in nonirradiated U salts. The spontaneous fission half-life of U238 can also be calculated from these data. Radiochemical procedures have been developed for the determination of each fission product, in which a quantity ranging from 0.1 to 1 disintegration/sec of the fission product activity is isolated from kilogram quantities of U salts, purified, and then counted. Where the half-life of the fission product was several months, U minerals instead of U salts, were used. Removal of the bulk of the U by a liquid extraction method was found to be necessary and/or advantageous in most cases, although it was possible to precipitate certain fission products directly from a concentrated solution of the U salts. A new procedure is currently under investigation for the isolation and quantitative determination of the isotopes of Ce by a liquid-liquid extraction method. Ce(IV) can be extracted from a 10 M HNO3 solution by a 1 to 4 mixture of TBP and CCl4 with high extraction efficiency, and further purified by a combination of oxidation-reduction and liquid-liquid extraction procedures.