Finite element based fuel performance investigation of U₃Si₂–FeCrAl design under normal and RIA conditions

U₃Si₂–FeCrAl system has been a promising Accident Tolerant Fuels (ATFs) candidate for its higher thermal conductivity, higher uranium density and lower oxidation rate. As a part of wide efforts to analyze the thermo-mechanical behaviors of the proposed ATFs, a finite element-based fuel performance code called BEEs, developed based on MOOSE (Multiphysics Object-Oriented Simulation Environment) framework, has been extended to analyze the behaviors of U₃Si₂–FeCrAl under reactivity insertion accidents (RIA). In this work, CABRI-REP tests were simulated to validate the modeling capacity of BEEs for RIA firstly. Then, with the fuel behavior models applicable to U₃Si₂ and FeCrAl implemented in BEEs, the thermo-mechanical response of U₃Si₂–FeCrAl to postulated RIA conditions were evaluated and compared with UO₂-Zircaloy, UO₂–FeCrAl and U₃Si₂-Zircaloy systems. The results show that U₃Si₂–FeCrAl system can reduce the fuel temperature (about 400–600 K) and delay gap closure during normal operation. The performance of cladding in U₃Si₂–FeCrAl system is comparable with UO₂-Zircaloy and UO₂–FeCrAl systems. However, the fuel central temperature of U₃Si₂–FeCrAl system is found to increase (about 110–180 K when RIA occurs at zero burnup, and about 170–190 K when RIA occurs after normal operation) compared to systems with UO₂ fuel due to the lower volumetric heat capacity of U₃Si₂, which can lead to a threat to fuel security in RIA conditions, especially taking the lower melting point of U₃Si₂ (U₃Si₂ is ∼1938 K and UO₂ is ∼3138 K) into account.