RESEAL II. A large scale in situ demonstration test for repository sealing. Final report on laboratory tests (WP1)

The RESEAL project aims at demonstrating the sealing with bentonite of a borehole and a shaft in plastic clay on a representative scale. The backfilling and sealing of shafts and galleries is an important part of underground repository designs. Any opening created during the repository construction is a potential preferential pathway for water, gas and radionuclides migration, and has to be effectively sealed afterwards. This report describes the laboratory work to characterise the shaft pellet/powder bentonite mixture seal, carried out by CEA (France), SCK•CEN (Belgium) and CIEMAT (Spain). It has been divided in two groups of activities, those aimed at the study of the hydro-mechanical properties of the sealing material, and the activities related to the determination of the migration parameters. To analyse the hydration mechanisms of the pellet/powder mixtures and their coupling with the mechanical behaviour, different infiltration tests with measurement of the swelling pressure have been performed. In addition, since the migration of radionuclides in clays is controlled by diffusion, the determination of radionuclides diffusion coefficients, as well as their accessible porosity, has been undertaken.