Les résultats de ce projet se sont traduits par une amélioration de la capacité à modéliser, à l’échelle moléculaire, la diffusion des radionucléides les plus mobiles (anions, cations alcalins et alcalino-terreux) et leurs interactions avec les surfaces des particules d’argile présentes dans la roche. À une échelle supérieure, les études menées sur la complexité de l’espace poral et de l’agencement minéralogique de la roche ont permis de comprendre comment ces caractéristiques influent sur les propriétés de diffusion (coefficient de diffusion effectif, tortuosité, anisotropie) des radionucléides.

Pour en savoir plus : http://cordis.europa.eu/publication/rcn/16388_en.html

The scope of the FUNMIG Integrated Project was to improve the knowledge base on biogeochemical processes in the geosphere which are relevant for the safety of radioactive waste repositories. An important part of this project involved the interaction between data producers (research) and data users (radioactive waste management organisations in Europe). The aim thereof was to foster the benefits of the research work for performance assessment, and in a broader sense, for the safety case of radioactive waste repositories. For this purpose a specifically adapted procedure was elaborated. Thus, relevant features, events and processes (FEPs) for the three host rock types, clay, crystalline and salt, were taken from internationally accepted catalogues and mapped onto each of the 108 research tasks conducted during the FUNMIG project by a standardised procedure.

My work was focused on the coordination of Sm and Eu in the montmorillonite interlayer, which was studied by neutron diffraction with isotopic substitution. It was found that the number of hydrogen atoms nearest to Sm and Eu were less than oxygen nearest atoms. This means that Sm and Eu are not surrounded only by hydration water molecules, but they are in contact with the oxygen siloxane atoms of the clay basal plane surface. It was found that the number of oxygen atoms of the clay surface giving a contribution to the total coordination number should be ≤ 3. Therefore, the deficit of hydrogen atoms in the first coordination shell of Sm and Eu should be explained supposing that the lanthanide cations are partially hydrolyzed.

The results from this research have important implications for Sm and Eu migration in clays, and their biogeochemical cycle . In addition to providing an improved understanding of hydratation and migartion processes in clays, this work has relevance to radioactive waste management.

<2008> Sobolev O., Charlet L., Cuello G.J., Géhin A., Brendle J., Hydration and hydrolysis of Sm(III) and Eu(III) in a clay interlayer: a neutron diffraction study with isotopic substitution Radiochimica Acta, 96(9-11), 679-683.

<2008> Sobolev O., Charlet L., Cuello G.J., Géhin A., Brendle J., Geoffroy N., Hydration and hydrolysis of Sm(III) in clay minerals: a neutron diffraction study J. Phyics.: Condensed Matter., 20(10), 104207.