The Study of Material Accountancy Procedure in Facilities Where Uranium Lower than Low Enriched is Treated

Material accountancy procedures were studied in D,N,LEU handling facilities by taking into consideration the material accountancy capability, measurement uncertainty practically available and so on. A significant quantity used by IAEA for low enriched uranium is \"75kg U-235 contained\". A loss of U-235 contained in uranium can be detected by two procedures, one is an U-235 isotope balance and the other is an uranium element balance. Facilities studied in this paper are a UF6 conversion facility, a gas centrifuge uranium enrichment facility, a fuel fabrication facility and a reprocessing facility where recycled uranium in addition to natural uranium will be processed in near future in Japan. The material accountancy capabilities were evaluated by taking into account both recycled and natural uranium. It was found that the material accountancy capability of an uranium element balance was almost always higher than that of an U-235 isotope balance under normal accuracy of a weight, a concentration and an enrichment measurement. Changing from a traditional isotope balance to an element balance for these facilities would lead to the substantial reduction of the resource of both IAEA and operators.