Steady-state thermoelectric coupling characteristics analysis of the thermionic space nuclear reactor based on OpenFOAM

Space nuclear power systems, particularly thermionic reactors, are regarded as essential technologies for deep space exploration due to their reliability, robust performance, long-life and theoretical potential for efficiency in extreme environments. However, a comprehensive understanding of their thermoelectric coupling characteristics remains incomplete. In this study, an analysis code is developed and validated, incorporating an optimized circuit model coupled with a reactor thermohydraulic system to enhance performance prediction. The results demonstrate high precision, with maximum temperature prediction deviations limited to approximately 15 K and current density variations constrained within 5.9 % across the operational range. The thermoelectric performance of the TOPAZ-II reactor under steady-state operations is analyzed, focusing on the spacecraft platform's load variation and thermal power parameters across various operating conditions. The results show that an increase in output voltage leads to a systematic reduction in the core structural material temperature, highlighting the intricate interplay between electrical and thermal performance. When the thermal input power is increased to 120 %, the electrical power output and thermoelectric conversion efficiency rise to 7.15 kW and 5.18 %, respectively. The steady-state analysis of TOPAZ-II identifies distinct performance modes under varying spacecraft platform loads and thermal inputs, providing a quantitative baseline for steady-state performance prediction and load-dependent characteristic evaluation.