Development of a transient analysis model for liquid metal cooled space nuclear reactor power system

Abstract

The space nuclear reactor power system (SNRPS), which uses a liquid metal-cooled reactor coupled with a closed-loop Brayton cycle for thermoelectric conversion, has emerged as the preferred choice for an advanced space power system. This preference is due to its excellent heat transfer efficiency in the core, wide power range, controllable equipment size, high power conversion efficiency, and mature technology. This study focuses on establishing a system transient analysis model for reactor design, control, and safety analysis of a SNRPS. The model includes subsystem models such as thermal–hydraulic models for the reactor core and primary coolant loop systems, power conversion unit models, and heat pipe radiator models. Six types of benchmark test problems are used to validate each sub-module and component model. The results show that the maximum absolute error between the sub-module model and the analytical solutions of these benchmark test problems is within 2%. Based on the theoretical model established, a transient analysis code for the space nuclear reactor (TACSNR) was developed. The TACSNR was verified using steady-state design parameters from the ultra-small liquid metal cooled space nuclear reactor power system concept (ULCR SNRPS) and the inherent safety sectored compact reactor with a SiGe thermoelectric (TE) power conversion assembly space nuclear reactor power system (SCoRe-TE SNRPS) startup transient process. The calculation results show that the maximum absolute deviation between the calculated values of the TACSNR and the steady-state design parameters of the ULCR SNRPS conceptual scheme is less than 1%, consistent with the parameter change trend and numerical values during the transient startup process of the SCoRe-TE SNRPS system. Additionally, the maximum relative deviation at rated steady state of the SCoRe-TE SNRPS is less than 12%.