Assessment of residual stress due to overlay-welded cladding and structural integrity of a reactor pressure vessel

Katsuyama, Jinya  ; Nishikawa, Hiroyuki*; Udagawa, Makoto; Nakamura, Mitsuyuki*; Onizawa, Kunio 

The residual stresses generated within the weld-overlay cladding and base material of reactor pressure vessel (RPV) steel was evaluated for as-welded and post-welded heat-treated conditions using thermo-elastic plastic creep analyses considering phase transformation. By comparing the analytical results with the experimentally determined values, we found a good agreement for the residual stress distribution within the cladding and the base material. It was shown that considering phase transformation during welding was important for improving the accuracy of residual stress analysis. Using the calculated residual stress distribution, we performed fracture mechanics analyses for an RPV during pressurized thermal shock events. We evaluated the effect of the weld residual stress on the structural integrity of an RPV. The results indicated that consideration of residual stress produced by weld-overlay cladding and PWHT is important for assessing the structural integrity of RPV.