Study on the influence of key thermal parameters on Brayton cycle operation performance of helium-xenon cooled reactor

[Background] The He-Xe Brayton cycle system that adopts helium-xenon mixture as the working fluid, has significant advantages of high cycle efficiency, high specific power, and great operation reliability, which has promising application prospects in the field of special nuclear power. The megawatt level special nuclear power that combined with helium-xenon Brayton cycle system and nuclear reactor, can effectively meet the needs of high-power energy supply, including deep space exploration, planet-base power supplement, and unmanned underwater vehicles. Presently, the research on the operation characteristics of the helium-xenon Brayton cycle system is insufficient and the systemically simulation models need to be developed urgently. [Purpose] This study aims to develop a steady-state simulation tool for helium-xenon closed Brayton cycles, enabling characterization of system components and overall configurations prior to actual engineering design and operation, thereby reducing research costs. [Methods] A simulation tool for steady-state analysis of the helium-xenon closed Brayton cycle was developed by establishing component models of key equipment in the thermodynamic system, including the heater, regenerator, cooler, turbine, and compressor. The accuracy of the simulation software was verified through comparison between design values from the U.S. "Prometheus" project and computational values obtained under identical conditions. With the output power fixed at 200 kW, the influences of critical parameters – including cycle maximum temperature, cycle minimum temperature, cycle maximum pressure, and total thermal conductivity of the regenerator on system efficiency and specific power were comprehensively analyzed. [Results] The calculation results of the helium-xenon thermodynamic cycle model developed in this work are in good agreement with the Prometheus’s design values, with the maximum node parameter error being 0.212% and the maximum system parameter error being 3.419%. The errors are within the acceptable error range. The accuracy and capability of the helium-xenon closed Brayton cycle model is verified. The results indicate that there is an optimal pressure ratio for both system efficiency and system specific power, but the optimal pressure ratios are not equal. In engineering design, the pressure ratio at the maximum system efficiency shall be adopted. A higher the maximum temperature and a lower the minimum temperature of the cycle will result in a higher system efficiency and specific power. The minimum temperature of the cycle has a more significant impact on the cycle efficiency than the maximum temperature. As the pressure ratio increases, the total thermal conductivity of the recuperator has a smaller impact on the cycle efficiency. [Conclusions] This study provides reference and basis for the design and optimization of helium-xenon closed Brayton cycle.