Sol-gel processing of fine fraction of UO2 sintered microspheres

The reaction mixture consisted of a 2M solution of uranyl nitrate and urea. Urotropine was added at 10 to 15 degC. Dispersing was effected by mixing in decalin, oil, silicon oil, and kerosene. Solidification was completed at a mixture temperature of 65 to 70 degC. In the decalin, silicon oil and kerosene media, regular gel particles of a spherical shape were formed while in oil gel spheres did not form. Various drying methods were tested, viz., at room temperature, at elevated temperature in a drying room, using an infrared lamp, azeotropic distillation. UO2 particles of a density higher than 98.5% of the theoretical value were prepared by reduction of xerogel particles with a mixture of argon-10% vol. hydrogen at a temperature of 850 degC and by sintering at 1200 degC. (H.S.)