Design And Analysis Of Passive Residual Heat Removal System For Molten Salt Reactor

The residual heat removal system is an important system in nuclear power plant, whose reliable operation is directly related to the safety of the reactor after shutdown. The design of passive residual heat removal system for molten salt reactor was presented in the paper. The system took full advantage of natural principle and removed the decay heat generated in fuel by air and water respectively. The steady-state performance characteristic of the passive residual heat removal system was simulated and analyzed with the self-developed code under C++ platform. Then the performance characteristic of the water-cooled system was calculated with the code of RELAP5.By way of natural circulation, the decay heat generated in the drain tank was transferred by air or water eventually after shutdown. This paper presented the system composition and described the features of the main equipment. According to the flow process, corresponding numerical models were constructed in the code of C++, the Lazarek-Black correlation was used to calculate the boiling heat transfer coefficient while when boiling happened in a large space MuxeeB method was employed. As to the condensation, the Akers correlation and the Nusselt formula were used to evaluate the condensation heat transfer coefficient horizontally and vertically. After calculation the performance of the system was got. Also the changes of system parameters such as system pressure and heat exchange power as well as temperature of the molten salt were obtained. The structural parameters sensitivity analysis was made with the code of C++. To extend the time that the temperature of the molten salt declines to freezing point, the regulation process was involved which either adjusted the number of the heat exchange tubes or the opening of the damper of the air funnel. Besides, the water-cooled system was simulated with RELAP5 code, thus got the operating characteristic of the system.The C++ program calculation result indicates that both of the schemes can transfer the decay heat and meet the design requirements. The heat transfer power reduces with the decay power decreasing and has self-regulation ability to some extent. The flow capacity and the heat transfer capacity can be effectively changed by adjusting the outer diameter of the thimble while it can't be realized by regulating the width of the gas space. The change of the number of the heat exchange tubes just affects the system pressure. Adjusting the height of the condensation circle has little influence on the flow capacity and heat exchange capacity. When changing the number of the thimbles in the drain tank to regulate the heat transfer power, the time that the temperature of the molten salt declines to freezing point is effectively delayed while changing the opening of the damper can't realize the goal. The calculation result of the RELAP5 code shows that the trend of the system performance is consistent with the result calculated with C++program.