A coordinated experimental and computational analysis was undertaken to investigate the temperature field, heat generation, and stress distribution within a spark plasma sintering (SPS) tooling-specimen system during single- and multipellet fabrication of uranium dioxide (UO2) fuel pellets. Different SPS tool assembly configurations consisting of spacers, punches, pellets, and a die with single or multiple cavities were analyzed using ANSYS finite element (FE) software with coupled electro-thermo-mechanical modeling approach. For single-pellet manufacture, the importance of the die dimensions in relation to punch length and their influence on temperature distribution in the pellet were analyzed. The analysis was then extended to propose methods for reducing the overall power consumption of the SPS fabrication process by optimizing the dimensions and configurations of tooling for simultaneous sintering of multiple pellets in each processing cycle. For double-pellet manufacture, the effect of the center punch length (that separates the two pellets) on the temperature distribution in the pellets was investigated. Finally, for the multiple pellet fabrication, the optimum spacing between the pellets as well as the distance between the die cavities and the outer surface of the die wall were determined. A good agreement between the experimental data on the die surface temperature and FE model results was obtained. The current analysis may be utilized for further optimization of advanced tooling concepts to control temperature distribution and obtain uniform microstructure in fuel pellets in large-scale manufacturing using SPS process.
Uranium dioxide - Molybdenum composite fuel pellets with enhanced thermal conductivity manufactured via spark plasma sintering
