MULTIPHYSICS ANALYSIS OF THORIUM-BASED FUEL PERFORMANCE UNDER REACTOR STEADY-STATE AND TRANSIENT ACCIDENT

摘要

The ThO_2 fuel has higher thermal conductivity and melting boiling point than the UO_2 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 Th_(0.923)U_(0.077)O_2 fuel and Th_(0.923)Pu_(.0.007)O_2 fuel have been implemented in fuel performance analysis code FRAPCON and FRAPTRAN. Finally, the performances of Th_(0.923)U_(0.077)O_2 fuel, Th_(0.923)Pu_(0.077)O_2 fuel and UO_2 fuel under both normal operating conditions and transient conditions (RIA and LOCA) are analyzed and compared. The Th_(0.923)U_(0.077)O_2 fuel is found to have lower fuel center-line temperature and the thorium-based fuels are observed to have a delayed pellet-cladding mechanical interaction (PCMI) under steady state. 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 conventional UO_2 fuel under both normal operating conditions and accident conditions.