Resilience assessment for nuclear power plants using Petri nets

Since the resilience issues encountered in nuclear power plants (NPPs) has not been explicitly addressed to date, Petri net models are developed in this paper to simulate the health states of relevant facilities, immediate responses, mitigation processes, and recovery and maintenance processes in an NPP. With the aid of the models developed, the resilience of the NPP is assessed with the consideration of the influence of ageing and the impact of external events. To demonstrate the methodology developed, it is applied to assess the resilience of a single-unit pressurised heavy-water reactor system to a station blackout accident. It has been shown that the methodology developed is effective in simulating and assessing the resilience of the NPP. It is also found that the ageing and proper maintenance of facilities that do not directly affect the operation of nuclear reactors are critical to the resilience of NPPs.