Study on probabilistic structural integrity assessment

Katsuyama, Jinya  

Structural integrity of major components in LWR is assessed conservatively with sufficient safety margin by deterministic way based on current regulation. For further safe long-term operation, structural integrity should be assessed scientifically and rationally without unnecessary over-conservatism. For this purpose, probabilistic fracture mechanics (PFM) analysis codes have been developed for weld-overlay cladding of reactor pressure vessel (RPV), and welded joints of pressure boundary piping. The effect of cladding on weld residual stress and probability of crack initiation during pressurized thermal shock were evaluated by PFM analysis. It was shown that weld-overlay cladding of RPV should be considered for structural integrity assessment. For piping weld, uncertainty of weld residual stress distribution due to scatter of welding conditions were evaluated. Applicability of PFM analysis to quantify the safety margin for the piping integrity assessment related to SCC was shown.