Synthesis of High-Density Pellets of Uranium Dioxide by Spark Plasma Sintering in Dies of Different Types

Abstract

A procedure for electric pulse consolidation of commercial UO₂ powders of various ceramic grades into high-density fuel pellets using dies of various types was studied. The influence of the parameters of spark plasma sintering (SPS) on the chemical composition of the initial powders and quality of ready UO₂ pellets was examined. The main advantages and drawbacks of the SPS process for consolidation of UO₂ powder in standard graphite dies were revealed. A novel alternative procedure for SPS of UO₂-based fuel pellets in Mo-based dies was suggested. High quality of the pellets (density 97.5–98.4% of theoretical, no C impurity, mean grain size no more than 3 μm) and mild sintering conditions (1100°С, 141.5 MPa, 25 min) make the process highly promising. The results obtained are of interest for the development and possible implementation of an industrial SPS process for production of ceramic nuclear fuel.