Fabrication method for UO2 pellets with large grains or a single grain by sintering in air

The effects of a powder treatment, the sintering temperature and the sintering time on the grain growth of UO2 pellets were investigated in air to obtain UO2 pellets with large grains. Air could be used for sintering because an oxidation path above 1803 K does not pass through a two-phase (UO2+x + U3O8−z) region. The UO2 pellets sintered by the CO2–air–CO2–H2 process consisted of a single grain or some large grains in the order of several millimeters.