Study on Densification Behaviour of UO2 Material Using Dilatometry

Abstract

High temperature dilatometer has been used for study on effect of various parameters on the shrinkage behaviour of the UO₂ powder compact. It is well known that the densification achieved on sintering is a function of powder characteristics, pressing and sintering parameters. For achieving sinter density in a close acceptable range it is required have a clear idea about the influence of these parameters on shrinkage characteristics. In the dilatometric laboratory tests, the linear shrinkage data from the dilatometer was obtained as a function some of these parameters. The runs were carried out in dilatometer under reducing atmosphere similar to production scale furnaces. Calculation of sintering rate exponent (n) was carried out and compared with literature data for the various possible sintering mechanisms like grain boundary diffusion, volume diffusion, surface diffusion etc. Microstructural features observed in the low density cases were correlated to the shrinkage behaviour in the dilatometer. The possibility of using a 'master shrinkage curve' for a given sintering cycle is explored. Comparison of the shrinkage curves for the lots before actual production with the master curve could be used as a screening test for the powder lots in order to predict the sintering behavior.