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In operating PWRs (Pressurized Water Reactors), incidents of Alloy 82/182 cracking increased the concern for structural integrity of butt weld locations recently, because of high weld residual stresses. Studies on PWSCC (Primary Water Stress Corrosion Cracking) have been mainly performed using deterministic approaches by controlling parameters, but a quantitative evaluation is difficult because of large uncertainties in each parameter and test results. The purposes of this paper are to provide a probabilistic fracture mechanics (PFM) analysis methodology and quantify failure probabilities for Alloy 82/182 welds in primary piping systems of nuclear power plants. To calculate failure probabilities, Monte Carlo simulation technique was used. To estimate the time to crack initiation, material susceptibility was quantified considering the effects of various processing, grain boundary carbide coverage, water chemistry including zinc addition, and so on. In crack growth analysis, crack orientation and the effects of water chemistry including dissolved hydrogen concentration were considered. And the effects of weld repair were evaluated.

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