Feasibility Study On Small And Medium Modular Light Water Reactors With Inherent Nuclear Safety And Security Features Using U3Si2 Fuel And MA

Small modular reactors (SMRs) have been paid much attention owing to their various potential applications and flexibility to various social demands. However, it is overloaded in safety and security, if the same grade regulation with large scale reactors are required for SMRs. Therefore, to introduce graded approach is important for reasonable and feasible regulation in SMRs. Uranium silicide (U3Si2) fuel has the higher heavy metal density, the thermal conductivity and chemical stability than U oxide (UO2) fuel, and it is expected to enhance the inherent safety and security features. 238Pu is produced from 237Np and 241Am by the nuclear transmutations, and its large decay heat and spontaneous fission neutron emission rates adverse effects of nuclear explosive devices (NEDs). The objectives of the present paper is to reveal the fundamental neutronics, nuclear safety and security features of small and medium PWR (SMPWR) by utilizing uranium silicide fuel and MAs. In fundamental neutronics and safety analysis, neutron transport and burn-up calculation were performed by MVP and MVP-BURN code with JENDL-4.0 cross section library. The results of the fundamental neutronics showed the U enrichment required to provide the same burn-up days in U3Si2 fuel was smaller than in UO2 fuel. In addition, due to the large neutron capture cross-sections of 237Np and 241Am, the initial reactivity and burn-up reactivity change of MA doped fuel was reduced. In the safety analysis, the temperature gradient inside U3Si2 fuel was smaller than in UO2 fuel due to the higher thermal conductivity of U3Si2 fuel. Material Attractiveness evaluations were conducted to evaluate the relative utility of nuclear materials to assemble NEDs for non-state actors in each phase of “acquisition”, “processing”, and “utilization”. The degree of influence in weapon utility was divided in 4 grades. The attractiveness of fresh and spent U3Si2 and UO2 fuel assemblies were equivalent. However, Pu separation in U3Si2 fuel was more complex and impractical compared with UO2 fuel. The decay heat from Pu in spent MA doped U3Si2 and UO2 fuel assemblies were enhanced due to higher ratio of 238Pu in MA doped assemblies.