Neutronic analysis of silicon carbide Cladding-ATF fuel combinations in small modular reactors

Abstract

With more attention being paid to the development of small modular reactors (SMR), the intrinsic safety issues have reached a critical point. Accident-tolerant fuel (ATF), such as the U3Si2, UO2-BeO, silicon carbide cladding etc. can maintain or improve fuel performance under normal reactor operating conditions and can maintain core integrity for a long period after the design-basis accident scenarios, providing a sufficient time margin to take measures. Therefore, applying the ATF to the SMR also enables the possibility of operating the SMR more safely. Most neutronic analyses of the ATF, however, have focused on the large-scale commercial pressurized water reactor. In this study, we adopted a given ATF design (the combination of U3Si2 and silicon carbide cladding) and compared it with other combinations of fuel and three different types of silicon carbide claddings in one single-fuel assembly and the full core of the mPower. We evaluated and analyzed the aspect of neutronic physics with Serpent-2 and OpenMOC computational codes. The results for the full core showed that the core life of U3Si2-SiC could be increased by 3.1% which feasibly could be used in the SMR from the neutronic point of view. The U3Si2, however, had a lower effect on neutron absorption than the UO2 when using the burnable poison rod in the full core. The neutronic penalties of different types of silicon carbide cladding were not significant in the SMR. Overall, the silicon carbide cladding-ATF fuel combinations were feasible for use in the mPower SMR.