Dissimilar metal welds (DMWs) involving Alloy 600 and its equivalent weld metal, such as Alloy 82 are used in a number of outlet feeders in CANDU® reactors. The higher operating temperature (∼300°C) leads to concerns that primary water stress corrosion cracking (PWSCC) might occur. This paper demonstrates the low rupture probability of DMWs due to PWSCC using probabilistic fracture mechanics (PFM) method with several critical assumptions validated by experiments. The leak-before-break is also demonstrated by comparison of the leak probability with rupture probability. A sensitivity study is carried out to investigate the effect of various factors on failure probabilities. Credible leak detection and action play an important role in limiting the rupture probability, while in-service inspection (ISI) has little effect to reduce rupture probability.

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