Verification of Station Blackout (SBO) Mitigation Capability for CPR1000 Nuclear Power Plants

To assess the mitigation capability of in-service nuclear power plants in China against a Station Blackout (SBO) as a design extension condition, this study conducts a simulation of the accident progression for a domestic CPR1000 unit based on a simulation platform. The study selects an SBO accident sequence initiated by a grid fault at full-power combined with a failure of emergency diesel generator start-up. By applying the unit’s accident procedures and simulating operator interventions, the transient behaviors of key parameters such as primary coolant system temperature, pressure, and core fuel temperature are analyzed. The results indicate that, under the coordinated response of automatic systems and procedure-guided operator actions, the existing mitigation measures can effectively maintain the unit in a safe and controllable state, thereby preventing its progression to a severe accident. Furthermore, based on deviation analysis between the simulation data and expected responses, this study proposes an optimization recommendation to “add a primary coolant system pressure monitoring module” to the procedures. Simulation verification demonstrates that this optimization can significantly reduce the risk of unintended accumulator initiation, thereby enhancing the establishment and reliability of natural circulation in the primary coolant during the accident.