MODIFICATION OF FROBA-THERMION AND ITS APPLICATION ON STEADY-STATE PERFORMANCE ANALYSIS OF SINGLE-CELL THERMIONIC FUEL ELEMENTS CONNECTED IN SERIES

The single-cell thermionic fuel element (TFE) is a promising candidate for the compact nuclear power system. Fuel mass transfer occurs due to high operating temperature. On the other hand, the single-cell TFEs are connected in series in the thermionic nuclear reactor. In view of the above challenge to the safety and efficiency of the single-cell TFE, the thermionic conversion model was modified and the circuit model was developed in FROBA-THERMION, a steady-state performance analysis code for the single-cell TFE. Further, a group of the single-cell TFEs connected in series was chosen and a steady-state performance simulation was carried out. The results indicate that the thermionic conversion efficiency will be decreased due to the emitter temperature change caused by fuel mass transfer. Influenced by the connection in series, the output voltage of the single-cell TFE with a higher emitter temperature is increased to match the output current of the one with a lower emitter temperature.