Dual-mode space nuclear power system based on a thermionic conversion reactor and thermoelectrochemical generator

Within the context of development of a transportation and power module for electrically-propelled delivery and subsequent long-term power supply of power-hungry functional equipment of a spacecraft, the paper provides the results of conceptual design studies into the feasibility of using a combined dual-mode nuclear power system with a thermionic conversion reactor and thermoelectrochemical generator. The feasibility of using a ThermoElectroChemical Converter (TECC) to generate electric power hinges upon the fact that TECC hot zone temperature lies within the range of temperatures of the lithium cooling system for the high-temperature lithium-niobium nuclear power system designed for the Hercules orbital transfer vehicle. The paper demonstrates the practicability of using a part of the heat radiating surface of the cooling system for the power system to place on it TECC elements. Within the thermionic reactor there is a zone of booster heat-producing elements that are cooled by a lithium coolant. Installed on the heat pipes of the heat-rejection system are TECC elements with the upper temperature of the thermodynamic cycle of about 1200 K and the lower temperature of about 500-550 K. Used as TECC working medium is sodium, the main structural material is niobium alloy NbZrC, the solid electrolyte is β-Al2O3. The above materials have a mix of properties that makes it possible to construct a highly efficient TECC operating within the specified range of temperatures. The paper provides performance data for the element and the entire generator with 30 kW electrical output.