Study on sintering kinetics and activation energy of UO2 pellets using three different methods

During early stages of sintering of UO2, diffusion of metallic ions plays the vital role as this is the rate controlling step of the sintering at that stage. Sintering kinetics and the activation energy at the early stages of sintering of UO2 in reducing atmosphere has been studied by several workers using different methods of calculation. The diffusion mechanisms that have been found to operate at this stage are grain boundary diffusion and volume diffusion. The activation energy calculated by different studies also varies widely. In the following study, sintering mechanism and activation energy for sintering of UO2 in reducing atmosphere has been studied by three different methods, namely, rate controlled sintering, constant heating rate and Dorn’s method. The kinetics of sintering and activation energy has been found to change with temperature. Initially grain boundary diffusion operates and in the later stage volume diffusion controls. Calculation of activation energy by the above methods shows that the rate controlled sintering and constant heating rate produces similar results, whereas the results of Dorn’s method are not quite matching.