A method to enrich reprocessed uranium with various initial contents of even-numbered isotopes

Nuclear industry needs effective recovering of fissile material from used nuclear fuel, as uranium accounting more than 90% of the spent nuclear fuel (SNF) volume. Use of reprocessed uranium (RepU) is associated with the difficulties due to the presence of ^232,234,236U isotopes in its composition. The content of these isotopes in fresh fuel is limited in accordance with specifications for low-enriched uranium (LEU). In this regard, in order to make a product of the required quality, it is necessary to modify the regular cascade scheme for enriching natural uranium and/or partially dilute the RepU with raw materials not containing ^232,234,236U (for example, natural uranium or depleted uranium). To solve such problems, a number of cascade schemes have been proposed for the last decades. However, there is still no answer what kind of scheme is preferable. In addition, most of them are unsuitable for full reuse of uranium extracted from spent fuel. Within the framework of the present paper, a double cascade scheme is proposed that allows a full use of reprocessed uranium (of any composition, including “dirty” one) in fuel production in compliance with restrictions on even-numbered isotopes. The “quasi-ideal” cascade, widely used in modeling separation processes in cascades for the separation of multicomponent mixtures, was chosen as the object of this theoretical study. The physical regularities of mass transfer in the proposed cascade scheme are analyzed. The interdependencies of cascade parameters are studied. It is shown that this scheme can be effectively employed to enrich the RepU of “dirty” composition, which are typical for SNF after several irradiation cycles.