Simulation-aided design of the negative-pressure exhaust system in HTGR nuclear power plants

Abstract High-temperature gas-cooled reactor (HTGR) nuclear power plants adopt an unpressurized vented confinement due to their inherent security. Negative-pressure exhaust systems (NPES) are therefore designed to maintain vacuum in the confinement so that radioactive gas and aerosol cannot pollute the atmosphere through exfiltration. For engineering applications, NPES should be shared by more than one cabin. The control strategy of NPES in the high-temperature reactor pebble bed module (HTR-PM), an HTGR demonstration project, is considered in this work. After describing the exhaust system with a mathematical model, a modular Simulink® simulation model is developed to aid in the design of the exhaust systems of HTGR nuclear power plants. Analysis of simulation results shows that (1) the volumes and airtightness of the cabins play dominant roles in the effectiveness of the control strategy. The time required to cut over between cases (time constant) can also affect effectiveness. (2) The control strategy of HTR-PM is effective, but when power plants increase in size, the control strategy becomes difficult to copy directly. (3) When an exhaust system with HTR-PM’s control strategy is applied to serve only one cabin with standard airtightness, its volume should be between 1300 and 46,000  m 3 to avoid misjudging accidents. (4) When an exhaust system with HTR-PM’s control strategy is applied to serve two cabins with standard airtightness simultaneously, the cabins’ volumes should be within the aforementioned range. (5) When three or more cabins with standard airtightness are served by one exhaust system simultaneously, the case can be simplified into the case with two cabins, and preliminary judgment of the effectiveness of HTR-PM’s control strategy can be obtained. (6) Our Simulink® model can be applied to study cases in which airtightness and the control strategy vary. Therefore, this model can be applied in the design of NPES of HTGR nuclear power plants.