Yuanzineng kexue jishu (Sep 2024)
Research on Design of Natural Circulation Decay Heat Removal for Pool-type Sodium-cooled Fast Reactor
Abstract
Based on the design parameters of the core decay heat removal through natural circulation of the typical high-power sodium-cooled fast reactor, using the system analysis program ERAC, a detailed analysis of the reactor core decay heat removal process characteristics after emergency shutdown was conducted, and comparative analysis was conducted on the cooling effects in the reactor under two sets of four conditions of decay heat removal system (DHRS). The results indicate that enabling DHRS requires thousands of seconds as it has a significant cooling effect on the core. During this period, the removal of core decay heat relies on the inherent thermal-hydraulic safety characteristics of the reactor. In principle, DHRS only needs to carry out the heat inside the reactor before the temperatures at the critical locations reaches its limit value, and keep the temperatures in a decreasing trend. When the independent heat exchanger (DHX) is arranged in the hot pool, the temperatures of the hot pool and the main vessel are relatively lower, which is beneficial for temperature control of the main vessel as the main circuit pressure boundary, and its effect is better than when arranged in the cold pool. In addition, different locating arrangements of DHXs will have an impact on the mass flow in the assembly wrappers and inter-wrappers, but the impact on the overall cooling effect on the core temperature is not significant. In order to reduce the investment and operating costs of nuclear power plants and then improve economic efficiency, it should be optimized on the natural circulation design of the pool-type sodium-cooled fast reactor. The optimization direction is to fully utilize the inherent thermal-hydraulic safety characteristics of the pool-type sodium-cooled fast reactor, reduce the requirements for the start cooling time and the power of heat discharge of DHRS. It is feasible to consider arranging all DHXs in the heat pool, reduce their volume, and lowering their design value of heat dissipation power. Alternatively, without compromising safety, other more economical and convenient effective methods could be selected. These research results will provide important references for the natural circulation design of pool-type liquid metal reactors such as commercial fast reactor and integrated fast reactor in China.
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