Effects of plasticity on the stress intensity factor evaluation for underclad crack under pressurized thermal shock events

Katsuyama, Jinya  ; Huang, L.; Li, Y. ; Onizawa, Kunio 

When the structural integrity of reactor pressure vessel (RPV) under pressurized thermal shock (PTS) events is assessed, an underclad crack is postulated at the inner surface of RPV and the stress intensity factor (SIF) is evaluated for this crack. On the inner surface of RPV, cladding of stainless steel is overlay-welded as a means for corrosion protection. Because the cladding is a ductile material, it is important to evaluate the SIF considering the plasticity of cladding. A SIF evaluation method considering the effect of plasticity has been established in France. In this study, we examined the SIF evaluation method for underclad cracks during PTS transients. The elastic and elastic-plastic analyses based on the finite element method considering PTS events and inner pressure were performed using three-dimensional models including an underclad semi-elliptical crack with different geometry. We showed the conservativeness of plastic correction method based on the analysis results.