Fabrication of (Th,U)O2 pellets containing 3 mol% of uranium by gel pelletisation technique

Internal gelation process has been developed to prepare high density ThO2–3%UO2 pellets. The study indicated that by carefully controlling the feed composition and the heat treatment scheme, soft mixed oxide microspheres could be obtained which are amenable for pelletisation at relatively low compaction pressures (200–250 MPa). The green pellets could be sintered in air up to 97% of TD at 1350 °C. The fractured and polished surface of the pellets showed a smooth surface without any berry structure. The shrinkage behaviour of these pellets was also studied in Ar + 8% H2 atmosphere using a dilatometer. These studies revealed that the densification starts at a low temperature of 1100 °C. The SEM studies indicated uniform microstructure in the pellets with 3–5 μm grain size with uniform pores (∼1 μm) distributed homogeneously in the pellet.