Evaluation of weld residual stress near the cladding and J-weld in reactor pressure vessel head for the assessment of PWSCC behavior

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

Weld residual stress is the most important factors to assess the structural integrity of RPV since it affects crack initiation and growth behaviors. Inner surface of the RPV is protected against corrosion by cladding. At the J-weld of the vessel head penetrations, Ni-based alloys are used for weld material. After the fabrication process, the residual stress remains in such dissimilar welds after PWHT. The residual stresses were measured using the DHD method. Thermal-elastic-plastic-creep analyses considering phase transformation were also performed. By comparing analytical results with measured ones, it was shown that there was a good agreement of residual stress distribution. It was suggested that taking phase transformation into account was important to improve the accuracy of analysis. Using the residual stress distributions, PWSCC behavior was calculated using PFM analysis code. Effects of the residual stress and scatter of PWSCC growth rate on the crack penetration were evaluated.