Research on performance enhancement of nuclear fuel with SiC cladding by using high thermal conductivity fuels

摘要

The engineering application of the fuel rod system consisting of traditional UO2 pellets and SiC accident tolerant fuel (ATF) cladding is challenged by high fuel operating temperatures, large fission gas release rates and high risks of brittle failure of the cladding. In this study, a preliminary research was carried out for performance enhancement of the fuel rods consisting of SiC cladding by replacing UO2 with high thermal conductivity fuels, including UO2/BeO, U3Si2 and UN/U3Si2. Thermo-mechanical modeling was conducted with the consideration of burnup effects for the three fuels with high thermal conductivity. An upgrade of the nuclear fuel analysis code FRAPCON4.0 was conducted to extend the simulation capability by implementing the new fuel models. Thermomechanical behavior of the original and improved fuel rods was simulated by the upgraded FRAPCON4.0. The simulation results show that using high thermal conductivity fuels can significantly reduce the fuel temperature and fission gas release. Furthermore, the fuel gaseous swelling is greatly mitigated due to the reduced fuel temperature, which is beneficial to prevent SiC cladding from brittle failure caused by pellet-cladding mechanical interaction. By comparison, UN/U3Si2 fuel presents the most promising and desired thermo-mechanical performance among all high thermal conductivity fuels investigated in this study.