Geochemistry of Callovo-oxfordian argillite at 80 °C : batch experiments and modeling

Hélène Gailhanou (1) , Stéphane Gaboreau (1) , Mathieu Debure (1) , Philippe Blanc (1) , Sylvain Grangeon (1) , Nicolas C.M. Marty (1) , Jean-Marc Greneche (2) , B Madé (3) , Scott Altmann (3) , Christophe Tournassat (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 IMMM - Institut des Molécules et Matériaux du Mans
3 ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs

A repository of high-level nuclear wastes in the Callovo-Oxfordian (COx) clay rock will lead to a temporary increase in temperature locally around the disposal cells, up to about 80°C. Thermally induced modifications of the pore-water chemistry of the clay rock must be assessed since the pore water chemistry can affect the rates of corrosion of metallic materials used in the disposal facility (Gaucher et al., 2009; Altmann, 2008). In the present study, carried out as part of a collaborative BRGM/Andra research program, the results of long-term batch experiments performed at 80°C, are compared with compositions predicted using a model based on the one developed for 25°C. These experiments include a previous study (Gailhanou et al., 2012) that is completed by recent long-term batch experiments in order to verify the reproductibility of results and better understand the reactivity of the COx rock-solution system at 80°C. In this aspect, selectivity coefficients for exchange reactions Na/K, Na/Ca, Na/Mg and Na/Sr in the clay-porewater system have been acquired at 80°C and have been considered to model the experiments.

Domaines: Géochimie

Hélène Gailhanou, Stéphane Gaboreau, Mathieu Debure, Philippe Blanc, Sylvain Grangeon, et al.. Geochemistry of Callovo-oxfordian argillite at 80 °C : batch experiments and modeling. Clays in Natural and Engineered Barriers for Radioactive Waste Confinement - 6th International Conference, Mar 2015, Bruxelles, Belgium. ⟨hal-01119495⟩