Characterization and densification studies on ThO2–UO2 pellets derived from ThO2 and U3O8 powders

ThO2 containing around 2–3% 233UO2 is the proposed fuel for the forthcoming Indian Advanced Heavy Water Reactor (AHWR). This fuel is prepared by powder metallurgy technique using ThO2 and U3O8 powders as the starting material. The densification behaviour of the fuel was evaluated using a high temperature dilatometer in four different atmospheres Ar, Ar–8%H2, CO2 and air. Air was found to be the best medium for sintering among them. For Ar and Ar–8%H2 atmospheres, the former gave a slightly higher densification. Thermogravimetric studies carried out on ThO2–2%U3O8 granules in air showed a continuous decrease in weight up to 1500°C. The effectiveness of U3O8 in enhancing the sintering of ThO2 has been established.