Development of evaluation curves for the structural integrity in the dissimilar metal welds against PWSCC in nuclear power plant

Recently primary water stress corrosion cracking (PWSCC) has occurred in nuclear power plant worldwide. In case PWSCC is observed during inspection, it needs the evaluation of structural integrity, which takes much time and effort and affects the outage period. For the fast evaluation and judgment whether the plant can be operated for further cycle, the KHNP-CRI are developing the evaluation curves for structural integrity against PWSCC in dissimilar metal weld regions in the plant. Those regions that alloy 82/182 were used as weld metal are the scope of this project. The reactor head penetrations and dissimilar butt welds in the nozzles are typical susceptible regions to PWSCC. For the development of evaluation curves, finite element analyses for weld residual stress are performed. Besides the weld residual stress analysis, the calculation of stress intensity factor through thickness and assessment of crack velocity and instability of remaining ligament are also conducted. Current status and results of this project are shown this paper