Influence of oxidation-reduction process cycle of uranium oxide on density and grain of U₃O₈ and UO₂ powders

Oxidation-reduction process of uranium oxide in a number of cycles has been investigated to determine the influence of oxidation-reduction cycle on the density and grain of U₃O₈ and UO₂ powders obtained from nuclear fuel recycling. In the first cycle, UO₂ powder obtained from the oxidation-reduction process of UO₂ sintered pellets was heated at various temperatures and time to form U₃O₈. The U₃O₈ powder was then reduced at temperature 850 °C for 2 hours in hydrogen atmosphere to convert it back to UO₂. The oxidation-reduction process was the second cycle. The UO₂ powder obtained was reoxidized to form U₃O₈, and the U₃O₈ was reduced back to UO₂ in the third cycle. In the fourth cycle, UO₂ obtained from the third cycle was oxidized to form U₃O₈. The densities and photographs of the two types of powders as the products of oxidation-reduction process were obtained. The results showed that the cycles of oxidation-reduction of uranium oxide influence the density and grain of U₃O₈ and UO₂ powders. In the third cycle, the powder density of U₃O₈ as the oxidation product is higher than those obtained in the first, second and fourth cycle. Similar trend prevails for UO₂ powder, the reduction product, up to the third cycle. Meanwhile the grains of both U₃O₈ and UO₂ powders tend to crowd together in the first cycle but then become smaller and separate in the following cycles. (author)