Processing of ThO2/CeO2 Ceramic Fuel

Abstract

The paper describes an effective procedure for mixing and conditioning ThO2 and CeO2 powders so they are suited for pressing and sintering into high‐density (Th0.9,Ce0.1)O2 ceramic pellets – this material being a “pilot” for (Th,Pu)O2 fuels. Wet ball milling with an organic dispersant aided the powder dispersing process by reducing the agglomeration of very small oxide particles. Homogeneous elemental distributions were seen within the calcined powder mixture. Heat treatments were applied to the calcined, mixed ThO2/CeO2 mix to study phase and surface area transformations. Solid solution formation commences at around 1300°C and goes to completion at a temperature of 1500°C. We also report the effect of a granulation strategy that can be applied to the production of high quality, mixed ThO2 nuclear fuel ceramics. Sized granules of blended ThO2/CeO2 powder were produced from precompacted disks of this material that were subsequently heat treated. This had a positive effect on die filling and compaction into green pellets, as well as on final sintered (Th,Ce)O2 pellet density. The microstructure of the sintered (Th,Ce)O2 ceramic was characterized using SEM‐based electron back‐scatter diffraction from which a uniform density and grain size were readily apparent. XRD results showed that a single phase Th0.9Ce0.1O2, fuel ceramic had been produced. Its density was ~94% TD.