Electrochemical dissolution of U_1-yGd_yO_2±x: Effect of Gd doping on various oxidation state of UO_2±x matrix

SNF (Spent nuclear fuel) is consisted with mainly UO₂, radioactive fission products and actinides species. Because the major radio nuclides are located within the oxide matrix, their release rates to the groundwater will be depended on the fuel corrosion/dissolution rate. The oxidation of UO₂ doped with RE (Rare earth) element has been investigated expensively for decades, in order to determine the effect of fission product impurities present in solid solution in used fuel. RE doped UO₂ shows enhanced stability of the cubic fluorite structures of U₄O₉-type with respect to U₃O₈-type depending on the sintering atmosphere as compared to un-doped UO₂. Such substantial efforts have been done, integrated research of stoichiometry and Gd-doping effects have received little interest. And also, there are difficulties to handle the nuclear fuel carefully not to spoil the intrinsic properties of itself. Especially, in determining dissolution behaviors of fuel, electrochemical techniques are very powerful and reliable tool to establish the thermodynamic values presented dissolution kinetics. Stoichiometric and non-stoichiometric Gd-doped U_1-yGd_yO_2±x pellets are prepared by mechanical blending method adjusting the oxygen potential. Stoichiometry of all pellets was confirmed by nondestructive X-ray analysis