Multiphysics analysis of thorium-based fuel performance under reactor normal operating and accident conditions in a light water reactor

Abstract

The ThO2 fuel has higher thermal conductivity and melting boiling point than the UO2 fuel, which is beneficial to the fast removal of heat and the improvement of fuel melt margin. In this paper, the material properties and thermodynamic behaviors of thorium-based fuel were firstly reviewed, and then the thermal physical properties and the fuel behavior models of Th0.923U0.077O2 fuel and Th0.923Pu0.077O2 fuel have been implemented in fuel performance analysis code FRAPCON and FRAPTRAN. Finally, the performances of Th0.923U0.077O2 fuel, Th0.923Pu0.077O2 fuel and UO2 fuel under both normal operating conditions and transient conditions (both RIA and LOCA) are analyzed and compared. The thorium-based fuels are found to have lower fuel centerline temperature than that of the UO2 fuel under normal operating condition, and a delayed pellet-cladding mechanical interaction (PCMI) under both normal operating and transient conditions. Furthermore, the fission gas release, cladding strain and internal fuel energy under transient conditions are found to be lower too. Lastly, the cladding displacement and temperature under transient conditions are also compared. The thorium-based fuel was found to have a higher safety margin and accident resistance than the UO2 fuel under both normal operating condition and transient accident conditions.