Development of MCTFE: A computer modeling code for single and multicell cylindrical thermionic fuel elements

This paper presents the modeling efforts undertaken to develop a computer code that is able to perform coupled thermal-hydraulic and thermionic analysis for both single and multicell Thermionic Fuel Elements (TFE). The code developed, given the name MCTFE (for multicell thermionic fuel element), is a steady-state finite element code specifically designed to analyze cylindrical TFEs. It employs an iterative successive-over-relaxation solution technique to solve for the temperatures throughout the TFE and a coupled thermionic routine to determine the total TFE performance. The calculated results include: the temperature distributions in all regions of the TFE, the axial interelectrode voltages and current densities, and total TFE electrical output parameters including power, current and voltage. MCTFE generated results are presented that compare experimental data from the single cell Topaz-II type TFE and multicell data from the General Atomics 3H5 TFE in order to benchmark the accuracy of the code methods