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.