Extending the Prediction of the Thermodynamic Properties of Clay Minerals to the Trapping of Trace Elements

The thermodynamic properties of clay minerals, which control the stability of these minerals in solution, are still a matter of debate in spite of recent advances (Gailhanou et al., submitted). This is especially the case for the minerals that may structurally include trace elements and potential radionuclides such like Ni, Cd, Co, Cr, Mn, Pb, ... The usual methods developed in order to predict thermodynamic properties are parameterised using a given set of minerals. For clay minerals, the latter are mainly composed by Si, Al, Fe and Mg, apart from the alkalis elements (Chermak and Rimstidt, 1989), which means that predictions are limited to minerals whose layers are composed by Si, Al, Fe and Mg. At the vicinity of H&ILW disposal cells, the possible interactions between clay rock or engineered barrier and waste degradation products can result in the appearance of clay minerals that may structurally include radionuclides within an irreversible trapping process. This work aims at proposing a method for predicting the thermodynamic properties of such minerals.