EFFECT OF OXYGEN ON THE OPERATION OF A SINGLE-CELL THERMIONIC FUEL-ELEMENT

The operation of thermionic converters (TICs) has been shown to be inf luenced by the presence of tracer amounts of oxygen in the cesium vapo r filled interelectrode gap. The induced changes, however, depend on t he oxygen and cesium partial pressures and the materials and temperatu res of the electrodes. The effects of oxygen on the loss rate from a t ungsten emitter surface, by sublimation and formation of volatile tung sten oxides, as a function of oxygen partial pressure were investigate d. Results showed that the deposit of the tungsten oxides on the coole r collector affect the converter performance, owing to the induced cha nges in the collector's oxygenated-cesiated work function and the effe ctive emissivity of the electrodes. Parametric analyses were performed which investigated the effects of introducing tracer amounts of oxyge n in the interelectrode gap on the performance parameters of a fission -heated single-cell Thermionic Fuel Element (TFE). These parameters ar e the electrodes work functions and effective emissivity, the TFE volt -ampere characteristics, the axial distributions of the current densit y and the electrodes temperatures, and the tungsten loss rate from the emitter surface. (C) 1998 Elsevier Science B.V. All rights reserved.