Study on reactor residual heat removal method based on steam controllable discharge in station blackout accident

Abstract

The design of passive residual heat removal system (PRHRS) has the problems of uncontrollable coolant cooling rate and incomplete matching between the heat removal capacity and the reactor residual heat. To solve these problems, a residual heat removal method is proposed in this paper, which is controllable release of secondary steam into the environment at the early stage of reactor shutdown when the residual heat is large. The feasibility of this method is verified by the thermohydraulic analysis code. The results show that this method can discharge the residual heat in a period of time after the reactor shutdown, and the coolant system can establish a stable natural circulation. But when the steam generator is empty, the residual heat must be removed by other ways. After that, based on the critical flow theory of nozzle, a simplified method for calculating the steam discharge power and estimating the safety-related parameters by steam pressure is proposed, which can be a reference for operators to control the cooling rate, analyze the system status and handle the accident. The conclusions can also provide references for the study and improvement of residual heat removal method.