Cation diffusion and crystal growth at the UO2-PuO2 interface

A better understanding of the homogenizing phenomena involved in the dry route fabrication of MOX fuel has led to the study of interdiffusion coefficients of plutonium and uranium during the sintering. Interdiffusion coefficients have been calculated from electron microprobe analysis of diffusion couples UO2 (green compact)/ PuO2 (green compact). A series of these diffusion couples has been sintered at 1773, 1873 and 2023K during 0 to 50 hours and under controlled oxygen potential (-88, -95 and -125 kcal/mol). The results show that grain-boundary diffusion predominates, essentially at the end of the intermediate stage of the sintering. On the opposite, the lattice diffusion is very slow. The sintering and particularly the crystal growth enhance the interdiffusion coefficients which are slightly greater compared to those of polycrystalline diffusion couples. (author). 6 refs, 5 figs