Development of maintenance significance evaluation method considering effect of pipe failure. Part 1. Proposition of evaluation method for maintenance index and construction of fluid leakage evaluation facility

Since several safety-related systems were added to the nuclear power plants (light-water reactors) through the process of the new regulatory requirements, the number of components to be inspected in service, which has been already large, will increase more than ever after the restart. Effective measure will be required to reasonably assign limited resource to maintenance activities. The authors have proposed the evaluation method for maintenance index to aim optimization considering influence of fluid leakage behavior with pipe failure, mainly targeting non safety-related piping and components. In this research, maintenance methods (time based maintenance, condition based maintenance, extraction of maintenance region utilizing the prediction code etc.) are to be selected based on maintenance significance which is evaluated with pipe failure probability and pipe failure impact to surrounding components and operators. To evaluate pipe failure impact, experimental facility which can investigate fluid leakage behavior with pipe failure has been constructed. Using this facility, we can conduct a mock test of flashing and steam flow leakage from various flaw geometries of pipe (crack, pinhole and guillotine break). (author)