A cost-benefit-risk study of the best (in terms of plant valuation) long-term strategy for canopy seal weld leakage control and prevention including a span of options for reactor vessel head J-Groove weld failures is performed. The range of options goes from the “do nothing” option up to replacement of the reactor vessel head with new control rod drive mechanisms. The results are presented in form of net present values for the options cost and include uncertainties for long-term costs associated with the options activities and prediction of failure rates for control rod drive mechanisms canopy seals and J-Groove welds. Results of this study rely on catching leaks during an outage and not during operation (mid-cycle). The consequence associated with a mid-cycle leak is much higher than for one found during an outage. This tends to indicate rigorous visual inspections during outages to ensure repairs are made during refueling outages. Thus, the effect of forced outage due to mid-cycle leak detection is not included to avoid strongly biasing the results in favor of reactor vessel head replacement.

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