Accelerated dissolution of doped UO 2 -based model systems as analogues for modern spent nuclear fuel under repository conditions

Systematic single-effect dissolution studies were carried out on the dissolution behaviour of pure and Cr- or Nd-doped UO 2 reference pellets as model materials for spent nuclear fuel with varying doping levels, densities, and grain sizes as well as of industrially produced Cr- and Cr/Nd-doped UO 2 pellets. The results were obtained from accelerated static batch dissolution experiments performed under strictly controlled conditions using H 2 O 2 as simulant for radiolytic oxidants formed due to the alpha-irradiation of water. The results indicate that the addition of Cr and the consequential modification of the fuel matrix does not lead to a significant change of the dissolution behaviour of these model materials compared to pure UO 2 reference materials. Contrarily, the dissolution rates of Nd-doped pellets are significantly lower than those of pure and Cr-doped pellets. These results provide additional insights into the influence of doping on the dissolution behaviour of modern spent light water reactor fuels under the post-closure conditions expected in a deep geological repository. Graphical abstract