A Modified Temperature-Dependent Elastoplastic Constitutive Model for Blister Growth in Irradiated Al6061 Cladding

Plate-type fuel elements generate large amounts of fission gases under irradiation, and the resulting cladding blistering caused by fission gas accumulation compromises both fuel integrity and nuclear reactor safety. Up to now, there appears to be insufficient understanding of blister growth behavior under varying temperature conditions. Therefore, for increased accuracy and safety, we develop a modified quasi-static finite-element model incorporating a bilinear isotropic hardening law and temperature-dependent degradation of elastic modulus and yield strength for post-irradiation Al6061 cladding. As temperature rises from 300 K to 600 K under 30 MPa internal pressure, concurrent mechanical degradation increases blister height by +20.0% and plastic strain by +21.6%, with the rate accelerating nonlinearly. Neglecting temperature-dependent elastic modulus overestimates the yield initiation pressure by up to 17.2% at 600 K, giving a non-conservative overestimation of the safety margin. Crack radius drives blister height in a near-exponential manner, whereas initial blister height has a limited effect. The modified framework proposed in this study provides a quantitative reference for the reliability assessment of plate-type fuel elements under irradiation and for blister failure prediction and safety evaluation of similar metallic claddings.