The contribution of swelling to self-sealing of claystone studied through x-ray tomography

Many countries, as among others France, Belgium and Switzerland, are facing the issue of finding a proper solution to store radioactive waste coming from nuclear power plants. The possibility them in underground tunnels is largely considered investigated. In Andra (Agence Nationale pour la gestion des Déchets RAdioactifs) selected Callovo-Oxfordian clay rock situated Meuse/Haute Marne site between 400 600 m depth possible host deposit. excavation storage expected create fractured zone around galleries. factures will be then gradually re-saturated by water surrounding they self-seal contact with water, thanks swelling potential COx. capacity self-sealing, i.e. closing fractures after possibly restoring permeability, thus primary interest for safety system respect gas solutes transport. physical mechanisms driving this phenomenon mainly de-structuration matrix present claystone. work, self-sealing response COx was investigated through x-ray tomography at multi-micrometre sub-micrometre voxel size. objective study influence mineralogy, size discontinuity, hydraulic paths, mutual orientation bedding plane fractures. discontinuity importance determining percentage closure. Fractures parallel more likely seal anisotropic occurs perpendicular plane. main novelty represented direct local observation process down scale lower than 1 μm.