Thermo-mechanical performance of petal-shaped fuel rods based on accident tolerant fuel cladding

Accident-tolerant fuel (ATF) cladding enhances nuclear fuel performance under extreme accident conditions. Current research on applying ATF cladding to petal-shaped fuel rods (PSFRs) for performance improvement remains exploratory. This study establishes a finite element-based thermo-mechanical coupling model to analyse PSFR behaviour under irradiation. The thermal–mechanical performance of Cr-coated, FeCrAl-coated, Zr-1%Nb, and FeCrAl claddings was investigated under normal operation and reactivity-initiated accident (RIA) conditions to evaluate their potential for replacing conventional Zr-4 cladding. Results indicate that thermal creep is the primary factor driving performance differences among cladding materials. Cr/FeCrAl-coated PSFR exhibited minor deviations from the reference model in stress, strain, and temperature distribution. While FeCrAl cladding demonstrated superior deformation resistance, it displayed earlier plastic strain initiation. Zr-1%Nb achieved significantly lower cladding stress (15.6 MPa at 5 % FIMA) owing to its excellent creep rate, highlighting its advantage in stress management. However, creep-induced radial deformation necessitates either increasing the gap between fuel rods or localizing the cladding thickness at petal angle to mitigate dimensional impacts.