(GRS-703) Investigation of Claystone / Bentonite Mixtures as Barrier Material for Geological Disposal of Radioactive Waste

C.-L. Zhang, A. Rogalski, B. Zehle, U. Hertes

Crushed Opalinus claystone, MX80 bentonite, and claystone/bentonite mixtures were investigated as engineered barrier material in a radioactive waste repository in the clay formations. Safety-relevant properties and performance of the selected barrier materials were determined under repository-relevant conditions, including

petrophysical properties (minerals, grain distribution, water content, etc.)
water absorption and retention capacity
compressibility for fabrication of compacted blocks
swelling pressure in relation to dry density
water permeability in relation to dry density
gas migration behaviour under water-saturated conditions
thermo-hydro-mechanical behaviour.

The research work was funded by the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV) under contract number 02E11627 and was carried out in the GRS Geolaboratory in the period from November 2017 to October 2022. Extensive valuable results were achieved, which are presented in this report. In general, the claystone/bentonite mixtures investigated exhibit favorable properties and performance. The test results can be used to design the engineered barriers in a repository.