High-resolution neutronics model for 238Pu production in high-flux reactors

Abstract

We proposed and compared three methods (filter burnup, single energy burnup, and burnup extremum analysis) to build a high-resolution neutronics model for 238Pu production in high-flux reactors. The filter burnup and single energy burnup methods have no theoretical approximation and can achieve a spectrum resolution of up to ~ 1 eV, thereby constructing the importance curve and yield curve of the full energy range. The burnup extreme analysis method combines the importance and yield curves to consider the influence of irradiation time on production efficiency, thereby constructing extreme curves. The three curves, which quantify the transmutation rate of the nuclei in each energy region, are of physical significance because they have similar distributions. A high-resolution neutronics model for ²³⁸Pu production was established based on these three curves, and its universality and feasibility were proven. The neutronics model can guide the neutron spectrum optimization and improve the yield of ²³⁸Pu by up to 18.81%. The neutronics model revealed the law of nuclei transmutation in all energy regions with high spectrum resolution, thus providing theoretical support for high-flux reactor design and irradiation production of ²³⁸Pu.