Analysis of sintering behaviors in Er-doped UO2

Defect equilibrium equations were modelled, and the relations of po2 versus x were derived using the mass action law. The dominant defect species active in a specified region were determined by fitting the curve of experimental data to the calculated curve of log po2 versus log x for each theoretical model. The calculated curve for (2:1:2) and (Er'U')x in the hyperstoichiometric U1.Y EryO2+x and that for (2Er'Vo')xdec in the hypostoichiometric U1-YEryO2-x are in good agreement with the present experimental results. The sintering behavior of Er-doped UO2 is observed with erbium content in oxidizing and reducing atmospheres. For sintering in oxidizing atmosphere, sintered density decreases as increasing y in U1-Y eRYo2+x . However, in hydrogen atmosphere, sintered density decreases as increasing y at lower erbium content but the density increases again above y=0.01. In oxidizing sintering conditions, the formation of (Er'U')x clusters hinders the diffusion of cations, and hence the sinterability of Er-doped UO2 decreases. In reducing atmosphere of Er-doped UO2 for higher Er concent , the oxygen vacancies make (Er'U')2 cluster decompose by charge compensation and the concentration of mobile cations increases, thereby improving the sinterability