Probabilistic structural integrity assessment of reactor coolant pressure boundary piping. 2. Residual stress analyses of the effect of scatter of welding conditions

Stress corrosion cracking (SCC) in primary loop recirculation piping made of austenitic stainless steel has been observed near welding joints. The SCC grows near the welding zone mainly due to high tensile residual stress by welding as well as the other contributing factors of material and environment. The residual stress analysis due to welding of austenitic stainless piping is important and has been already conducted by many researchers. In present work, the effect of scatters of welding conditions such as heat input and welding speed on residual stress have been evaluated by parametric FEM analyses considering the variation of some parameters based on the welding experiments. The effects of welding conditions on crack growth behavior have been also evaluated by SCC growth simulations using calculated residual stress distributions and a procedure in the fitness-for-service code. Welding parameters such as heat input and welding speed have a strong influence on crack growth rate since residual stress is also affected by scatter of these welding parameters. (author)