(GRS 556) In-Situ Research Work of GRS at the Mont Terri Rock Laboratory and Related Modelling - Experiments HE-E, FE-M, DM-A, SB-A, DB, MB-A, Virtus

K. Wieczorek, O. Czaikowski, L. Friedenberg, K. Jantschik, M. Komischke, M. Kröhn

Operation of nuclear power plants creates heat-generating radioactive waste which, according to international consensus /OEC 08/ and to the concepts most countries using nuclear power are developing, should be disposed of in deep geological formations. In different countries, different host rocks are considered owing to their respective geological situations. In Germany, a decision on the host rock has not yet been taken – rock salt, claystone, and crystalline rocks are under investigation.

The overall objective of nuclear waste disposal in geological formations is to ensure permanent containment of the waste, concentrating and isolating it for very long time from the biosphere. Claystone has a very low permeability, and water pathways are naturally closed by plastic deformation and swelling. Although claystone in its natural state is water-saturated, transport processes are dominated by very slow diffusion processes. This makes claystone a candidate host rock for a repository, and several European countries (e. g., France, Switzerland, Belgium) have developed repository concepts in a clay environment.