Study on Mitigating Capability of High-Pressure Safety Injection for Large Break LOCA in PWR

Talking a typical Westinghouse three-loop pressurized water reactor （PWR） as reference plant and using the PWR severe accident analysis platform based on RELAP/SCDAPSIM code, best estimate calculation of hot leg large break LOCA of 25 cm without mitigating measures is performed. The mitigating capability of high-pressure safety injection to the accident is studied when peak core temperature reaches 1 100 K, 1 300 K and 1 500 K respectively. The results show that the time of starting high-pressure safety injection plays an important role in the accident progression. Injection during early stage will prevent core from melting effectively. However, injection during later stage may deteriorate the progression of severe accident and result in accelerated melting.