Some aspects of the separation of nuclear fission products by liquid-liquid extraction

The technique for and methods of separation of products of nuclear fission play a major role in many stages of the nuclear fuel cycle. The extraction of these products from effluent solution after the processing of the burnt-up nuclear fuel is receiving considerable attention. Trivalent lanthanoides are usually extracted together with Am(III) and their mutual separation is rather difficult. The extraction of lanthanoides with tertiary amines or quaternary ammonium salts involving the benzyl group as one of substituents has been studied in order to find the influence of the alkyl chain length on the extraction selectivity and capacity. Suitable extractants for the separation of Am(III) and Ln(III) from the acidic nitrate solutions were recommended. Using vapour phase osmometry and cryoscopy the association of these compounds was measured at 5.25 and 50 deg C allowing a rough estimation of medium association degree for the formation of the aggregates. The method of apparent molar volumes, supplemented by the spectrophotometric method, was used for identification of the chemical composition of the aqueous phase. (author)