Effect of the Microstructural Morphology on UO2 Powders

Several UO2 powders with different morphologies were synthetized and characterized. Three different morphologies were synthesized thanks to sol gel process (big heap of about 200μm wide consisting of sintered crystallites) on the one hand, and to oxalic precipitations (one square platelet morphology and one hexagonal stick morphology) on the other hand. Significant differences in dissolution kinetics were observed. Therefore, the morphology of the powders was found to be a key parameter that has to be considered in studies of UO2 dissolution kinetics. The second part of the study consists in dissolving in nitric acid in in the same operating conditions three UO2 powders having different crystallites sizes. It was shown that dissolution kinetics is dependent on the morphology but also on the powder stoichiometry.