Research on mitigation strategies for multi-unit nuclear power plants under extreme conditions of long-term loss of external power supply

As the rapid increase in the number of nuclear power units operating in China, the operation mode of multi-unit large-scale nuclear power bases at the same site has become more common. There are differences in the extreme conditions of long-term loss of external power supply and the response strategies of single-unit. Based on the typical pressurized water reactor multi-unit at a domestic site, this paper analyzes the constraints faced by the units to maintain safety without external resource support under the condition of losing external power supply, and proposes targeted "large isolated island" operation and implementation methods, while also proposing follow-up research directions for the weaknesses in this operation mode.