Improvements to PFM analysis code PASCAL and some case studies on RPV integrity during pressurized thermal shock

Onizawa, Kunio ; Shibata, Katsuyuki; Osakabe, Kazuya; Tanaka, Kazuhisa

Probabilistic fracture mechanics (PFM) analysis code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed at JAEA to evaluate the conditional failure probability of a reactor pressure vessel (RPV) containing a flaw under transient conditions such as pressurized thermal shock (PTS). Some functions of PASCAL have been improved such as Monte Carlo method, probability of crack detection (POD) by inspection and the GUI. Using the improved PASCAL, case studies on some parameters for some typical PTS transients have been performed. When the crack existence probability for the Marshall- and PNNL-type distributions is considered, the failure probability could be the same order of magnitude. The effect of chemical composition of vessel material was studied through the comparison of conditional failure probabilities for some transients. The effect of POD by inspection was also compared and evaluated in terms of inspection time.