Evaluating the proliferation resistance of plutonium in Light water reactor spent fuel from recycled reprocessed uranium

This study evaluates the proliferation resistance (PR) of plutonium in spent nuclear fuel (SNF) from re-enriched reprocessed uranium (RepU) recycling in Light Water Reactors (LWRs). The focus is on Pu denaturing via 236U accumulation during recycling. Two distinct recycling approaches, direct RepU enrichment and blending enriched RepU (ERU) with enriched natural uranium (ENU), were analyzed using SCALE/TRITON code and matched abundance ratio cascade (MARC) model. Results indicate that Pu denaturing is feasible for less experienced states when the accumulation of minor U isotopes is unrestricted in direct enrichment. However, this method raises safety and radiological concerns making it irrelevant in practice. Conversely, blending ERU controls minor U isotopes but fails to significantly improve PR. Neither approach satisfactorily meets the desired PR criteria within current regulatory frameworks. These findings highlight the need to reassess standards in RepU recycling, suggesting future research aiming at achieving a balance between resource utilization and nonproliferation.