Crystallization characteristics of ammonium uranyl carbonate (AUC) in ammonium carbonate solutions

Ammonium carbonate solutions with an excessive amount of NH3 were produced in a commercial AUC (ammonium uranyl carbonate) conversion plant. In this study the AUC crystals, precipitated with uranyl nitrate and ammonium carbonate solutions prepared in the laboratory, were characterized to determine the feasibility of recycling ammonium carbonate solution. The AUC crystals were easily agglomerated with the increasing concentration of CO32− and mole ratio of NH 4 + CO 3 2− in ammonium carbonate solution. Effects of a mixing system for the solution in the AUC crystallizer and the feed location of the solution on the agglomeration of AUC crystals were also studied along with the effects of agglomerated AUC powders on UO2 powders. Finally, the feasibility of manufacturing UO2 fuel with a sintered pellet density of 10.52 g/cm3, using the AUC powders generated in this experiment, was demonstrated.