Probabilistic fracture mechanics analysis of reactor pressure vessel with underclad and through-clad cracks under pressurised thermal shock transient

Semi-elliptical underclad cracks resulting from the fabrication process of a reactor pressure vessel (RPV) were able to be detected by non-destructive testing method. Meanwhile, after long-term operation under severe conditions, such as high temperature, high pressure, and irradiation, the RPV becomes brittle and susceptible to damage, especially when subjected to pressurised thermal shocks (PTS). Therefore, the probabilistic fracture mechanics (PFM) analysis of RPV with the crack should be applied to evaluate the operation safety. To the best of the authors' knowledge, few studies or computer codes have applied PFM analysis for such cracks. Therefore, this study conducts PFM analysis for cracks by modifying the calculation procedure of FAVOR 12.1 computer code. The results show that during the lifetime of a nuclear power plant, such cracks will not threaten the RPV's safety. Additionally, three methods were proposed to improve FAVOR 12.1's ability to perform PFM analysis for axial through-clad cracking.