A one-dimensional code of double-coupled passive residual heat removal system for the swimming pool-type low-temperature heating reactor

In Swimming Pool-type Low-Temperature Heating Reactor (SPLTHR), the Passive Residual Heat Removal System (PRHRS) is an indispensable part of the reactor safety system. In the heat transfer process of the PRHRS system, the natural convection heat transfer outside the Passive Residual Heat Removal Heat Exchanger (PRHR HX) in the reactor pool has a great influence on the flow and heat transfer characteristics of the system. In this study, an experimental facility was built to study the natural convection heat transfer outside the tube bundle under low temperature difference. According to the experimental results, a PRHRS for SPLTHR was designed. And a double-coupled natural circulation system analysis code was developed to investigate the start-up characteristics of the system under different initial conditions. The research results showed that the correlation of Yang predicts the experimental heat transfer results well. The calculation results indicated that the designed system met the heat removal requirements after reactor shutdown. If the temperature in the pipeline between the Passive Residual Heat Removal Heat Exchanger (PRHR HX) and the air-cooler was linearly distributed, the system would quickly establish a natural circulation and reduced the number of oscillations before the system reached stability. At the air-cooler, when the temperature of the heat transfer fluid in the water side changed, the temperature and mass flow rate of the air loop would quickly follow the change. The designed system and calculation results can provide a design basis for engineering applications.