Characterization of ThO2-UO2 pellets made by co-precipitation process

The co-precipitation technique renders an excellent route to obtain a homogeneous mixture of ThO2 and UO2 powders. In this process, after the nitrate solutions of Th and U are mixed in the intended ratio, oxalic acid is added for co-precipitation. The precipitate is then dried and calcined to get a solid solution of ThO2 and UO2. In this study, ThO2-30%UO2 and ThO2-50%UO2 (% in weight) powders were characterized in terms of particle size, particle shape, surface area, phase content, O/M ratio etc. The pellets obtained by sintering these powders were characterized with the help of optical microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The XRD data for ThO2-30%UO2 and ThO2-50%UO2 pellets showed the presence of a small amount of U3O8 phase besides fluorite phase. The grain size of ThO2-30%UO2 and ThO2-50%UO2 was found to be 5.7 and 4.5 μm, respectively.