Optimisation of the engineered barrier system

Emplacement of technical barrier bentonite as highly densified blocks (foreground) and granulate (background)
Emplacement of technical barrier bentonite as highly densified blocks (foreground) and granulate (background)
© Comet Photoshopping GmbH, Dieter Enz

Here we test technologies involved in storage of containers, backfilling of storage tunnels with bentonite, and sealing of the tunnels. The extent to which the barrier effect of Opalinus Clay might be reduced by the possible development of hydrogen gas as a consequence of the corrosion of the steel containers is still debated. Other materials, such as copper, ceramics, and new designs for the containers will be tested and evaluated in the rock laboratory in the future. The effects of elevated temperatures and gas pressures over longer periods on the transfer characteristics of bentonite and Opalinus Clay are targeted for detailed elucidation. The overriding goal is to understand linked processes: to properly grasp the effects of building procedures, operation, and closure of a disposal site, we must consider the hydraulic, thermal, mechanical and geochemical processes not in isolation but in combination and under conditions of mutual interaction.

Results and applications

All findings to date from the Mont Terri rock laboratory confirm that closed systems in clay layers remain intact over geological time periods. These results are not just of interest for the storage of nuclear waste, the same measurement methods and safety designs are also applicable to the storage of non-degradable chemical waste. Furthermore, in the future, underground storage of carbon dioxide – an important greenhouse gas – could become significant. In this context, argillaceous rocks could well be crucial for sealing purposes.