Production of more ideal uranium trioxide microspheres for the sol-gel microsphere pelletization process without the use of carbon

Renewed interest by the U.S. Department of Energy in the sol-gel microsphere pelletization process led to an evaluation of dried uranium trioxide (UO₃) microspheres produced without the use of carbon by the internal gelation process at Oak Ridge National Laboratory. An earlier study has shown that less dense UO₃ microspheres led to uranium dioxide pellets with higher densities. This effort identified feed formulations that produced dried UO₃ microspheres with the lowest tap densities for gelation temperatures of 333, 343, 353, and 363 K. The tap densities of these dried UO₃ microspheres ranged from 680 to 820 kg/m³, which were significantly lower than the previously reported low UO₃ density of 900 kg/m³. This study confirmed an earlier observation that the effects of gelation conditions on the properties of the gel sphere are complex since only two of the four best formulations were similar in composition. The need to age the wet gel spheres in the gelation medium for 20 min at the end of the experiment was also confirmed.