Neutronic analysis of thorium-uranium mixed fuel for multi-application small light water reactor (MASLWR)

Abstract

In this work, a neutronic analysis estimation of a Multi-Application Small Light Water Reactor (MASLWR) core with the minimum possible modifications in the geometry will be presented. In this study, many cases are investigated, in the first case the reactor core is fuelled by uranium with enrichment 4.95 %. For the second case the reactor core is fuelled by uranium with enrichment 4.95 % and a mixture of 50 % uranium and 50 % thorium. For this case, five different core distributions are modeled. For the third case, a seed and blanket design is investigated where the middle positions of each assembly are fuelled with 4.95 % enriched UO₂ while the boundary positions are fuelled once with 50 % ThO₂ + 4.95 % enriched UO₂ and second with 30 % ThO₂ + 4.95 % enriched UO₂. MCNP6 code has been used to calculate neutronic parameters such as effective multiplication coefficient (K_eff), cycle length for reactor core, the nuclear fuel evolution during the burnup, total neutron flux, kinetic parameters such as delayed neutrons fraction and prompt neutron lifetime and finally, the power peaking factor of the MASLWR different cores. The results show that the utilization of thorium fuel improves the overall performance characteristics of the MASLWR without burnable poisons. The results are compared with the uranium core enrichment 4.95 %. All thorium cases have better conversion and longer reactor cycle and higher fuel burn-up, and the most attractive feature is its resistance to nuclear proliferation.