Benchmark analysis on probabilistic fracture mechanics analysis codes concerning multiple cracks and crack initiation in aged piping of nuclear power plants

Li, Y. ; Osakabe, Kazuya*; Katsumata, Genshichiro; Katsuyama, Jinya  ; Onizawa, Kunio ; Yoshimura, Shinobu*

Multiple cracks in the same welded joints have been detected in piping systems of nuclear power plants. Therefore, structural integrity assessments considering multiple cracks and crack initiation in aged piping have been important. Probabilistic fracture mechanics (PFM) is a rational methodology in structural integrity assessment of aged piping in nuclear power plants. Two PFM codes, PASCAL-SP and PRAISE-JNES, have been improved or developed in Japan for the structural integrity assessment considering the age related degradation mechanisms of pipes. In this paper, a benchmark analysis was conducted considering multiple cracks and crack initiation, in order to confirm their reliability and applicability. Based on the numerical investigation in consideration of important influence factors such as crack number, crack location, crack distribution and crack detection probability of in-service inspection, it was concluded that the analysis results of these two codes are in good agreement.