Optimization of standby safety system maintenance schedules in nuclear power plants

A methodology and a computational scheme are developed based on dynamic programming (DP) to find the minimum cost maintenance schedule for nuclear power plant standby safety systems. Surveillance and testing are assumed to return the component to as-good-as-new condition whether accompanied by restorative maintenance only or full repair or replacement. The methodology defines component state as the number of unsurveilled and untested maintenance intervals or stages, and the optimization process is decomposed into (a) feasibility screening and (b) DP search. This approach achieves a significant reduction in the state space over which the DP search is to be performed. The application of the scheme is demonstrated on the ten-component high-pressure injection system of a pressurized water reactor. This demonstration indicates that the scheme is viable and efficient and particularly suited to exploit any economies of scale and scope that may be present.