Irradiation-thermal-mechanical coupled modeling of Pd-induced corrosion in SiC layer of TRISO fuel particle and failure behavior analysis

Based on the COMSOL multi-physics coupling platform, an irradiation-thermo-mechanical coupling performance analysis model for TRISO particles was established, and three simulation methods for Pd corrosion of the SiC layer were developed: the SiC layer thinning method, the deformed geometry method, and the activation method. By comparatively analyzing the simulation effects of the three methods under different steady-state conditions (1 073 K, 1 273 K, and 1 473 K), the influence of Pd corrosion on the stress distribution of the coating layers and the failure probability of the SiC layer was systematically evaluated. [Results] The results indicate that the activation method more reasonably reflects the stress evolution behavior between the IPyC and SiC layers and provides the best simulation performance among the three methods. Under an accident transient condition (temperature increase from 1 073 K to 1 873 K sustained for 1 000 h), the Pd corrosion depth increases significantly at high temperature. Coupled with the increase in internal particle pressure, the hoop stress of the SiC layer shifts from compressive to tensile, leading to a marked increase in the failure probability. With a safety limit of failure probability not exceeding 1×10⁻⁴, the allowable residence time of TRISO particles under this accident condition should not exceed 300 h.