Influence of the alpha radiation on the UO2 dissolution in high pH cementitious waters

To assess the long-term behaviour of spent fuel in conditions of the Belgian Supercontainer design, dissolution tests were performed to determine the solubility and dissolution rate of depleted and Pu-doped UO2 in synthetic cement waters. The results confirm the behaviour generally observed with UO2 at neutral pH in absence of H2. Due to the radiolysis of water, the produced oxidizing species oxidise the U(IV) to U(VI), inducing an increase of the uranium concentration. Consequently, the dissolution rate increases from the depleted UO2 to the most active doped UO2. Imposing a H2 overpressure had no significant effect on the UO2 behaviour. (author)