Risk-Informed Method for Predicting the Operation Life Extension Period of Active Safety Systems at Nuclear Power Plants

Abstract

An original method has been developed for predicting the operation life extension period of thermal mechanical equipment of safety systems based on the assessment of the residual resource by the number of thermohydrodynamic and mechanical cyclic loads and the test frequency during design operation life. Based on the developed method, as well as the results of technical inspection of pump and armature bodies of emergency core cooling and steam generator emergency feedwater systems, it was found that the permissible operation life extension period is 4 years for the design test frequency, 8 years if the test frequency is reduced by 2 times, 16 years if the test frequency is reduced by 6 times, 20 years if the test frequency is reduced by 10 times. However, the possibility of reducing the test frequency requires additional substantiation for optimizing the test frequency, taking into account the effects of equipment wear and the accumulation of critical defects between tests. The need to optimize the test frequency de-termines the relevance of further research.