Thermal-hydraulic analysis of gas-cooled space nuclear reactor power system with closed Brayton cycle

Space nuclear reactor power system (SNRPS), especially megawatt power level, is very attractive for the future civil and military space demands. The high-temperature gas-cooled reactor coupled with closed Brayton cycle (CBC) can achieve high-power output for space applications. For the gas-cooled SNRPS with CBC, dynamic models for all components, including reactor, turbine, compressor, alternator, ducting, pump, recuperator, gas cooler and heat pipe radiator, are developed in this article. Then, a transient system analysis code (SAC-SPACE) is developed to perform the safety characteristics analysis of the SNRPS. In the full-power steady-state analysis, the maximum fuel temperature has a margin of 1323 K from the melting point. Moreover, the transient responses of the SNRPS under the mechanical failure of one Brayton loop (MFOBL1) and the reactivity insertion accident (RIA) are simulated and analyzed. During the MFOBL1, the maximum fuel temperature is 1275 K lower than the melting point, and finally, the reactor power stabilizes at 56.8% of the rated power. For the RIA, as long as the reactivity introduced into the core does not exceed 0.61 $, the SNRPS can reach a new steady-state safely by itself without other protection strategies. It can be concluded that the SNRPS has good self-stability due to the negative reactivity feedback of the reactor. This article may provide useful theoretical supports for the design and safety analysis of the gas-cooled SNRPS with CBC.