Development of CAP process for fabrication of ThO2–UO2 fuels Part I: Fabrication and densification behaviour

The coated agglomerate pelletization (CAP) process is a novel and innovative technique for the fabrication of (Th, 233U) mixed oxide fuel pellets. This technique is being investigated to fabricate the fuel for the forthcoming Indian Advanced Heavy Water Reactor (AHWR). In the CAP process, ThO2 is converted to free flowing agglomerate by powder extrusion route. As only ThO2 is handled to this stage, all the operations are carried out in a normal glove-box facility. Subsequent operations are carried out in a shielded glove-box or hot cell facility using manipulators. In this study, fabrication of ThO2–4%UO2 and ThO2–20%UO2 (all compositions are in weight percent) pellets was carried out by CAP process. For having these ThO2–UO2 pellets, ThO2 granules and U3O8 powders were used as the starting materials. The densification behaviour of the pellets was studied in reducing and oxidizing atmospheres using a high temperature dilatometer. The microstructure was examined by optical microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA).