A Dynamic Reliability Model for Damage Accumulation Processes

It is necessary to obtain a detailed understanding of the behavior of reactor components performing at elevated temperatures at normal reactor operation, during off-normal transients, and in accident conditions. The currently used approaches do not sufficiently unify the probabilistic description (reliability), mechanical analysis (fracture mechanics, etc.), and engineering correlations for component life prediction (time-temperature parameter methods). The dynamic equations governing the evolution of the material damage based on the physical model of reliability are formulated in a unified manner. The model permits interrelating the concepts of material strength, accumulated damage, and reliability in regard to their dynamics. The model is applicable for static loading conditions as well as stress—and temperature—transients. The model validity is checked by comparing model predictions with the actual static and transient test data for the fast reactor fuel element cladding (Type 316 stainless steel).