Effects of multi-recycling of uranium reprocessed from spent nuclear fuel on the proliferation resistance of plutonium and uranium

Abstract

The effects of re-enriching and multi-recycling reprocessed uranium (RepU) from the spent nuclear fuel of light water reactors on the proliferation resistance (PR) of Pu and U are studied. The presence of 236U and 238Pu enhances the PR of multi-recycled RepU. The 236U/235U ratio of RepU varies from 0.4 to 1.2, depending on the initial 235U enrichment and fuel burnup. 236U is co-enriched while re-enriching 235U in RepU. Based on the centrifuge enrichment data, the enrichment coefficient of 236U (α236), defined as 236U/235U ratio after and before enrichment, is 0.703, on average. The α236 value is utilized in a simple model to estimate the attainable maximum possible 235U enrichment for multi-recycled RepU. Estimations showed an increase in the PR of multi-recycled and re-enriched RepU, which was confirmed by matched-abundance ratio cascade model. The PR of Pu is enhanced in each recycle due to the increased production of 238Pu from 236U.