Résumé
In order to study the effects of the cationic distribution homogeneity on the life cycle of Th1-xUxO2 ceramics, including sintering and reprocessing (dissolution) steps, five different ways of preparation were set up, going from the most homogeneous solid solutions obtained through oxalic co-precipitation to a mechanical mixture of the parent oxides. Dilatometric experiments evidenced the better sintering capacity for the most homogenous compounds obtained through wet chemistry methods while dry chemistry routes led to poor density values (between 80 and 90 percentTD). However, the introduction of additional mechanical grinding step prior the sintering of the powders systematically led to the homogenization of the systems. Improved homogeneity also provide a better chemical durability associated with the congruent dissolution of thorium and uranium in solution during dissolution tests of Th0.5U0.5O2 samples. Conversely, heterogeneous samples led to incongruent behaviors that can be smoothed by introducing a grinding step prior the preparation of sintered samples. Since the impact of the cationic distribution homogeneity must be followed carefully during the study of the solid-solution interface evolution, in operando observations of evolving solid-solution interface by ESEM were performed during dissolution. They allowed imaging the preferential dissolution of uranium enriched zones and confirmed the important role of chemical heterogeneities present at the interface.