S. Choi S. Chirayath, “Investigation Of Proliferation Resistance Of Enriched Reprocessed Uranium Fuel Due To Higher Buildup Of Pu-238 At Discharge”, INMM and ESARDA Joint Annual Meeting, Virtual Meeting, August 23 – September 1, 2021.
Reprocessing of used nuclear fuel being the acquisition path for Pu by the proliferating states, the roles of intrinsic and extrinsic barriers to proliferation through this path need a deeper analysis. Denaturing Pu with higher fraction of 238Pu is one of the intrinsic barriers that renders Pu less attractive for a nuclear explosive device and at the same time does not affect its value as a fuel for electricity generation. Previous studies suggest that the presence of 238Pu fraction in excess of 6.2% in Pu provides high intrinsic proliferation resistance (PR). Hence, doping nuclear fuel with the precursors of 238Pu, such as 237Np had been recommended. A different precursor, 236U, and a relatively easy isotope to incorporate in nuclear fuel is the focus of this study. Enriched reprocessed uranium (ERU) contains higher 236U (due to its presence in the used fuel and its further enhancement after 235U re-enrichment) compared to natural or reprocessed uranium. This aspect can enhance intrinsic barriers against U and Pu proliferation while practicing the recycling of used fuel. Until this time, the verification of the PR of ERU has been conducted without a deeper understanding of the multi-isotope enrichment. ERU, containing multiple U isotopes, requires a different approach of enrichment calculation than the usual binary isotope method. Thus, to determine the concentration of 236U in ERU, we used a matched-abundance ratio cascade (MARC) model, which has the advantage of being independent of a particular cascade type. We modified the MARC model to embody a gas centrifuge cascade, the most suitable commercial technique to handle ERU. Following the MARC model, Monte Carlo N-Particle Transport (MCNP) computer code was used to simulate fuel burnup of a pressurized water reactor fuel assembly that uses ERU with an equivalent neutron reactivity as that of a usual low enriched uranium (LEU) fuel assembly. Both, uranium enrichment and fuel burnup simulations allowed us to estimate the 238Pu buildup in the ERU-based LWR fuel. Further computational work is in progress to compare the PR of ERU to the traditional LEU-based or mixed oxide (MOX) fuel recycling approach.