Optimal Neutron Spectrum Database for In-reactor 238Pu Production.

Abstract

Plutonium-238 (²³⁸Pu) is a scarce heat-source radioisotope used in nuclear batteries, which is produced by in-reactor irradiation of Americium-241 (²⁴¹Am) or Neptunium-237 (²³⁷Np). Optimizing the neutron spectrum can improve the production efficiency of ²³⁸Pu, but currently, it is still a lack of knowledge about the optimal neutron spectrum for ²³⁸Pu production. Genetic algorithms and burnup algorithms are combined to identify optimal neutron spectra for ²³⁸Pu production under various irradiation times and flux levels, and build an optimal neutron spectrum database, which answers the questions "What is the optimal neutron spectrum for ²³⁸Pu production?" and "What is the maximum efficiency for ²³⁸Pu production" once and for all. This database can be referred to for determining the optimal neutron spectrum, guiding the neutron spectrum regulation process to improve the yield of ²³⁸Pu. Moreover, these results find that the production method of in-reactor irradiation ²³⁷Np not only has a higher yield but also achieves a higher purity of ²³⁸Pu than that of in-reactor irradiation ²⁴¹Am, which conflicts with the traditional experiences, providing with previously unknown insights and helping break through the efficiency limit of traditional methods, maximizing ²³⁸Pu production.