Risk-informed decision making in the nuclear industry: Application and effectiveness comparison of different genetic algorithm techniques

Abstract

The risk-informed decision making (RIDM) process, where insights gained from the probabilistic safety assessment are contemplated together with other engineering insights, is gaining an ever-increasing attention in the process industries. Increasing safety systems availability by applying RIDM is one of the prime goals for the authorities operating with nuclear power plants. Additionally, equipment ageing is gradually becoming a major concern in the process industries and especially in the nuclear industry, since more and more safety-related components are approaching or are already in their wear-out phase. A significant difficulty regarding the consideration of ageing effects on equipment (un)availability is the immense uncertainty the available equipment ageing data are associated to.This paper presents an approach for safety system unavailability reduction by optimizing the related test and maintenance schedule suggested by the technical specifications in the nuclear industry. Given the RIDM philosophy, two additional insights, i.e. ageing data uncertainty and test and maintenance costs, are considered along with unavailability insights gained from the probabilistic safety assessment for a selected standard safety system. In that sense, an approach for multi-objective optimization of the equipment surveillance test interval is proposed herein. Three different objective functions related to each one of the three different insights discussed above comprise the multi-objective nature of the optimization process. Genetic algorithm technique is utilized as an optimization tool. Four different types of genetic algorithms are utilized and consequently comparative analysis is conducted given the different features of the algorithms. The results obtained from the optimization show that by applying risk-informed surveillance requirements a significant reduction of system unavailability is achievable. The advantages and disadvantages among the four different types of genetic algorithms applied are addressed as well.