Preparation of UCO sols suitable for gelation into microspheres by sol–gel process with glucose

The design, development, and fabrication of fuel elements characterized by their safety, reliability, extended service life, and high burnup capabilities constitute a critical component within the scope of fourth-generation reactor research and development endeavors, the uranium carbon oxide (UCO) fuel stands out with its superior thermal conductivity and a higher uranium content compared to the more traditional uranium dioxide, making it an ideal candidate for these advanced nuclear reactors. The fabrication of such uranium-based fuel kernels hinges on a crucial step, which is the preparation of the uranium sol, which significantly affects the dispersion of the gel particles and, ultimately, the quality of the final products.

The objective of this study was to prepare UCO ceramic microspheres using glucose as a carbon source by the external gelation method combined with carbothermal reduction. Additionally, the results demonstrated that uranium sol could be dispersed into gel spheres at a reaction temperature of 80 °C, the molar ratio of urea to uranium (CO(NH₂)₂/U(VI)) is between 3.1–3.3, and the uranium concentration of 1.6–2.4 M. Moreover, adding an appropriate amount of tetrahydrofurfuryl alcohol was proven effective in resolving the cracking issue observed in the gel spheres. Finally, UCO ceramic microspheres with homogeneous microstructures could be prepared through appropriate dispersion and heat treatment.