Simulation of fission heated single-cell thermionic fuel elements in presence of oxygen using uniform electric heating

Abstract

This paper investigated the accuracy of simulating fission heated single-cell Thermionic Fuel Elements (TFEs) using uniform electric heating in the presence of oxygen in the interelectrode gap. The electrodes temperatures current densities, and the tungsten loss rates from the emitter surface were calculated and compared for both heating options. The effect of oxygen presence in the interelectrode gap on the TFE performance was also compared for fission and electrically heating TFE. Electrical heating results in a more uniform axial distributions of emitter temperature, current density, and tungsten loss rate distributions in the central part of the TFE compared to fission heating. Results show that introducing oxygen into the interelectrode gap reduces the output electric power for both fission and electrically heated TFEs. For example, at an effective oxygen pressure of 5×10−9 torr and O/W atom ratio in the tungsten oxides deposits on the collector surface of 0.66, the electric power output at Qth=3500 Wth was about 38 We less than in the absence of oxygen, for both electrically and fission heated TFEs.