Thermal safety analysis of thermionic space nuclear reactor startup on orbit

The complex cosmic thermal environment is a great challenge for the safe operation of space nuclear power into orbit. For liquid metal cooled space nuclear reactors, excessive heat dissipation before core start-up will cause pipe blockage. In this paper, models are established for the thermionic reactor including the radiator and orbit heat flux. A system analysis code is improved to analyze the characteristics of the reactor with a heat shield. Moreover, the self-check and start-up operation of TOPAZ II are proposed and analyzed. Numerical results show that the fluid of the reactor will freeze without a heat shield during the self-check process. After adding a heat shield, the maximum heat dissipation power is reduced to 141.2 W. In the start-up operation, casting the heat shield causes the heat dissipation power to rapidly increase from 0.1 kW to 1.7 kW.