Probabilistic Failure Analysis of SiC‐CMC/Nb Fuel Claddings Under Loss‐Of‐Coolant Accident Conditions

A numerical framework leveraging finite element analysis is established to examine the thermomechanical behavior and burst safety of a novel accident‐tolerant fuel (ATF) cladding design. This design incorporates a thin niobium (Nb) liner positioned between two layers of silicon carbide ceramic matrix composites (SiC‐CMC). The burst safety is assessed through a probabilistic failure analysis utilizing Weibull theory, accounting for the scatter in the apparent strength of SiC‐CMC and the associated size effect. By examining variations in Nb layer thickness and pellet‐clad gap thickness, the primary focus is on assessing the burst safety of the sandwich claddings in an APR1400 fuel system under both steady operation and loss‐of‐coolant accident (LOCA) scenarios. The findings indicate sandwich claddings are likely to function without fracture or leakage for both the original thickness (82.5 µm) and reduced gap thicknesses of up to 70 µm. However, a further reduction to 57.5 µm in gap thickness is likely to lead to cladding failure during steady operation. This research leverages computational modeling to gain a foundational insight into the thermomechanical performance of SiC‐CMC/Nb sandwich claddings in nuclear fuel rods and provides predictive tools aimed at augmenting the safety and reliability of next‐generation nuclear power plants.