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

Onizawa, Kunio ; Nishikawa, Hiroyuki; Ito, Hiroto

Probabilistic fracture mechanics (PFM) analysis codes for reactor pressure vessels (RPVs) and piping, called as PASCAL series has been developed at JAEA. The PASCAL2 code can evaluate the conditional probability of flaw initiation and fracture of an RPV under transient conditions such as pressurized thermal shock considering neutron irradiation embrittlement of the materials surrounding the reactor core of the RPV. Recent improvements of PASCAL2 are related to the treatment of weld-overlay cladding. The results of PFM analysis using the improved code have indicated that the residual stress by weld-overlay cladding affects the fracture probability of RPV. The results also indicate that the fracture toughness of cladding should be taken into consideration for the evaluation of realistic through-wall cracking probability. The PASCAL-SP code has been developed recently. The PASCAL-SP evaluates the probabilities of failures such as leakage and break 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, which affect SCC behavior, have been determined by parametric FEM analyses verified through comparisons with welding experiments and incorporated to the code.