Thermal-hydraulics and thermionic anaysis of TOPAZ-2 thermionic fuel element using hxtopaz

Extensive experimental data from TOPAZ-2 thermionic fuel element (TFE) provides an excellent opportunity for benchmarking of HXTOPAZ. Previous modeling of the TOPAZ-2 TFE with TFEHX does not includes the heat loss through the ends of the TFE and the effects of the performance of the scandium oxide spacers. Heat removal through the electrical leads changes the axial power distribution and, therefore, the emitter and collector temperatures hereby affecting the thermionic process. Heat conduction through spacers also decreases the emitter temperature in the proximity of the spaces. However, results from TFEHX showed a good agreement for a certain range of the thermal input power. To take into account these phenomena, a new computer code called HXTOPAZ is under development to include the effects of the electrical leads and the scandium oxide spacers. The new model uses both axial and radial power distribution to calculate the temperature field across the TFE.