Effect of oxygen on the operation of a single-cell thermionic fuel element

Abstract

The operation of thermionic converters (TICs) has been shown to be influenced by the presence of tracer amounts of oxygen in the cesium vapor filled interelectrode gap. The induced changes, however, depend on the oxygen and cesium partial pressures and the materials and temperatures of the electrodes. The effects of oxygen on the loss rate from a tungsten emitter surface, by sublimation and formation of volatile tungsten oxides, as a function of oxygen partial pressure were investigated. Results showed that the deposit of the tungsten oxides on the cooler collector affect the converter performance, owing to the induced changes in the collector's oxygenated–cesiated work function and the effective emissivity of the electrodes. Parametric analyses were performed which investigated the effects of introducing tracer amounts of oxygen in the interelectrode gap on the performance parameters of a fission-heated single-cell Thermionic Fuel Element (TFE). These parameters are the electrodes work functions and effective emissivity, the TFE volt–ampere characteristics, the axial distributions of the current density and the electrodes temperatures, and the tungsten loss rate from the emitter surface.