Study on UC Phase Control of UC Ceramic Microspheres Prepared by Sol-Gel Method

Since uranium carbide (UC) fuel has higher thermal conductivity and uranium density than UO2 fuel, good inherent safety and economy can be achieved by UC dispersion fuel. This paper focuses on the research of UC phase control during sol-gel preparation of UC ceramic microsphere. Using nano-carbon black powder as carbon source, UC ceramic microspheres were prepared by sol-gel process combined with carbothermal reaction process. Specific amount of carbon black was uniformly added into the glue solution, which was then dispersed to prepare carbon ADU gel spheres. With heat treatment of carbon ADU gel spheres subject to carbothermic reaction, ceramic microspheres containing UC phase were obtained. During the experiment, the effects of different carbon black addition ratio, thickener addition level and dispersion process on the chemical composition, sphericity and surface morphology on UC ceramic microspheres were investigated. The effects of heat treatment temperature, atmosphere and pressure on the preparation of UC microspheres were also studied during the carbothermic experiment. The process parameters for UC phase control were determined through the experiment and XRD, and the ceramic microsphere samples containing the UC phase were obtained as well. Analysis results show that crack-free UC microspheres with smooth surface can be obtained after drying when sol solution C/U is 2.5∼6.0 and thickener addition level is 1.2∼2.0 kg/kgU. By reaction treatment at high temperature, ceramic microspheres with good sphericity, compact structure and UC phase composition were obtained. A preparation method of UC ceramic microspheres was developed as a result.