Candu Energy Inc. (former commercial operation of AECL) has developed probabilistic tools to support nuclear plant operators with a risk-based fuel channel management strategy. One such tool is used to evaluate the probability of pressure tube rupture resulting from pressure tube to calandria tube contact and hydride blisters. This tool assumes that PT rupture occurs when delayed hydride cracking (DHC) initiates in a blister. The objectives of the probabilistic assessments are to:

• Determine the overall risk of PT rupture in the reactor core for comparison with the acceptance criteria.

• Determine the risk of PT rupture for specific fuel channels to assist in the development of an inspection/maintenance strategy.

• Evaluate the risk reduction that would result from different fuel channels inspection/maintenance scenarios.

• Optimize inspection/maintenance programs.

The distributions of the most critical input distributions can be derived by benchmarking against in-reactor measurements. Two benchmark methods were developed to take advantage of the recent advancements in the accuracy of the inspection tool that measures the gap profile between the PT and the CT.

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