Influences of heating processes on properties and microstructure of porous CeO2 beads as a surrogate for nuclear fuels fabricated by a microfluidic sol-gel process

Abstract

The control of microstructure is critical for the porous fuel particles used for infiltrating actinide nuclides. This study concerns the effect of heating processes on properties and microstructure of the fuel particles. The uniform gel precursor beads were synthesized by a microfluidic sol-gel process and then the porous CeO2 microspheres, as a surrogate for the ceramic nuclear fuel particles, were obtained by heating treatment of the gel precursors. The fabricated CeO2 microspheres have a narrow size distribution and good sphericity due to the feature of microfluidics. The effects of heating processes parameters, such as heating mode and peak temperatures on the properties of microspheres were studied in detail. An optimized heating mode and the peak temperature of 650°C were selected to produce porous CeO2 microspheres. The optimized heating mode can avoid the appearance of broken or crack microspheres in the heating process, and as-prepared porous microspheres were of suitable pore size distribution and pore volume for loading minor actinide (MA) solution by an infiltration method that is used for fabrication of MA-bearing nuclear fuel beads. After the infiltration process, 1000°C was selected as the final temperature to improve the compressive strength of microspheres. Keywords: Nuclear fuel, Microfluidics, Porous CeO2 microspheres, Heating processes, Microstructure