Development of probabilistic fracture mechanics analysis codes for reactor pressure vessels and piping considering welding residual stress

Probabilistic fracture mechanics (PFM) analysis codes for reactor pressure vessels (RPVs) and piping, called as PASCAL (PFM Analysis of Structural Components in Aging LWRs) series, have been developed. The PASCAL2 (PASCAL version 2) evaluates the conditional probability of fracture of an RPV under transient conditions including pressurized thermal shock (PTS) considering neutron irradiation embrittlement of the vessels. Recent improvements to PASCAL2 are related to the treatment of weld–overlay cladding. The results using the improved code indicate that the residual stress by weld–overlay cladding affects the fracture probability to some extent. The PASCAL-SP (PASCAL – Stress corrosion cracking at welding joints for Piping) evaluates the probabilities of failures including leakage and breaks of safety-related piping complying with Japanese regulation and rules. Effects of welding residual stress distribution as well as inspection accuracy are focused in this study. Residual stress distributions have been determined by parametric FEM analyses and incorporated into the code.