Burst Safety Analysis of Strengthened FeCrAl Claddings in APR1400 Fuel Rods Subject to LOCA Conditions

Abstract

Because of their greater accident tolerance, iron-chromium-aluminum (FeCrAl) alloys hold great promise for applications in nuclear fuel claddings. Here, a finite element-based computational framework is developed to analyze the thermomechanical performance of APR1400 fuel rods with FeCrAl claddings subjected to a typical LOCA condition preceded by 4 years of normal operation. The effect of enhancements in the yield and ultimate strength of FeCrAl on the burst safety of fuel rods is evaluated for various choices of pellet diameters and cladding thicknesses. The pellet diameter is increased by reducing the cladding thickness and/or the pellet-clad gap thickness with the intention of compensating for the additional neutronic penalty of FeCrAl in comparison to the conventional Zircaloy. It is found that a reduction of the pellet-clad gap thickness from 83 to 50 μm can increase the cladding's burst safety by up to 35%. Additionally, strengthening FeCrAl alloys has significantly improved cladding performance under LOCA (Loss of Coolant Accident) conditions. Specifically, an 80% enhancement in the yield and ultimate strength has been shown to improve the cladding burst safety by 80%. The findings of this study suggest that improved material properties and geometric modifications can significantly improve the burst safety of FeCrAl-based ATF systems, which is an important consideration for their practical implementation.