Behavior of Np, Pu, Am, Tc upon glass corrosion in a concentrated Mg(Ca)Cl2 solution

The objective of this investigation is to describe the extent to which Np, Pu, Am and Tc are mobilized from vitrified high-level radioactive waste into the near field of an HLW repository in a salt formation, when a hot and concentrated salt solution comes into contact with the glass. Waste form corrosion studies are conducted with a salt solution representing the composition of a fluid phase encountered in drill holes in the Gorleben salt dome. Test temperatures are determined by the designed maximum surface temperature of 200 C for the vitrified waste in the Gorleben salt. The following results were obtained: (1) pH changes of the radioactive leachate are the same as in inactive leachates; (2) the time and temperature dependence of the reaction for the radioactive glass are in excellent agreement with that of the inactive glass; (3) Np, Pu, Am, and Tc have not been reimmobilized in secondary minerals. Hence, mobilization of these radionuclides is governed by the kinetics of glass dissolution. Pu oxidation states were analyzed and related to Pu concentrations