In a pressurised water reactor nuclear power device, the primary loop system is a closed loop. Therefore, when the coolant in the loop undergoes temperature changes or volume fluctuations for some reason, it will inevitably cause corresponding changes in system pressure. If the loop pressure exceeds the design pressure, it will cause damage to the system and equipment; if the pressure drops too low, it will cause local boiling or pool boiling in the reactor core, leading to core burnout. Therefore, in order to ensure the safe and reliable operation of the pressurised water reactor nuclear power device, it is necessary to control and protect the pressure of the reactor primary loop system, which is the purpose of establishing a pressure safety system. The pressurizer is the main equipment of the pressure safety system.