Thermo-electric characteristics analysis of thermionic energy conversion in space nuclear reactors

Among static energy conversion technologies, thermionic energy converters have emerged as the preeminent choice for space nuclear reactor applications, distinguished by their high efficiency, compact architecture, and exceptional operational reliability. A comprehensive system analysis code, developed in C++, has been employed to integrate a thermionic electron emission model, an electric circuit model, and a thermionic conversion efficiency model. Through this code, thermionic characteristics for both single components and multiple components configured in series and parallel have been calculated, with validation indicating an error margin of less than 0.2 A/cm². The performance characteristics of an individual thermionic fuel element have been rigorously evaluated, and comprehensive sensitivity analyses have been conducted on both emitter and collector temperatures. Under steady-state conditions, a maximum power output of 9.32 kW has been demonstrated by series-connected elements, while parallel-connected configurations have achieved 752 W. Notably, in scenarios involving the loss of a heat sink, it has been observed that maintaining the operating voltage of parallel-connected elements below a specific threshold during the incident results in enhanced power output, thereby facilitating core cooling. This study provides critical insights into the optimization of design and performance for thermionic energy conversion elements in space nuclear reactor applications.