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

TLDR

Space nuclear reactor power systems at megawatt scale, especially high‑temperature gas‑cooled reactors coupled to closed Brayton cycles, are attractive for future civil and military space missions because they can deliver high power output. The study develops comprehensive dynamic models of all SNRPS components and aims to provide theoretical support for the design and safety analysis of gas‑cooled SNRPS with closed Brayton cycles. Dynamic models were implemented in a transient analysis code (SAC‑SPACE) that simulates component behavior and transient responses to mechanical failure of a Brayton loop and reactivity insertion accidents. Steady‑state analysis shows a fuel temperature margin of 1323 K from the melting point; during a loop failure the fuel temperature remains 1275 K below melting and power stabilizes at 56.8 % of rating, while a reactivity insertion below 0.61 $ leads to a safe new steady state, demonstrating the system’s self‑stability via negative reactivity feedback.

Abstract

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.