Deep Geological Repository Research

Deep geological disposal of high-level nuclear waste with retrievability is worldwide seen as the safest option for the isolation of this waste from the biosphere. The concept of a multi-barrier system includes the following barriers 1) waste (vitrified or spent fuel), 2) the canister (copper or stainless steel), 3) the geo-engineered barrier (bentonite or crushed salt depending on the host rock) and 4) the geological barrier. Through this concept of radionuclide isolation or retardation dose values in the evolution of the repository will be magnitudes below the dose limits set by the regulatory guidelines (0.1 mSv/a). Germany considers currently three different host rock types (rock salt, indurated sedimentary formations and crystalline rocks) potentially be suitable to host a deep geological repository. The comparison of sites with the different geology for the final decision will be a challenge. Investigations of the Applied Geology group focus in collaboration with KIT-INE on the integrity of the geo-engineered barrier under the influence of glacial melt water representing future glaciation periods (CFM and KOLLORADO-e2) and the mechanical evolution of this compacted bentonite over time and its homogenization via water saturation (BEACON). Further aspects are the mobility of radionuclides in the geosphere from the nanoscale to the macroscale including migration experiments in Underground research laboratories (URL’s) as the Grimsel Test Site (CH) or the Äspö Hard Rock laboratory (HRL). Groundwater migration processes include advection/diffusion/matrix diffusion and the role of organic/inorganic colloids/nanoparticles on contaminant retention.

New aspects investigated within the recently started joint project TRANS-LARA is the realistic description of the potential transport along the causal chain groundwater – unsaturated zone – soil – plant based on the mechanistic understanding gained through spectro-microscopic techniques and reactive transport modeling approaches using surface complexation models (SCM). The Applied Geology group will focus on the selenium and natural occurring radionuclides transfer groundwater – soil through the unsaturated zone as dissolved or nanoparticle associated species.

Project leader: Thorsten Schäfer, Dirk Merten, Arno Märten, 2x n.n.

See Project page: BEACON, KOLLORADO-e2, TRANS-LARA

Figure 1: View into the GTS tunnel of the controlled zone with the equipment of the CFM project and the megapacker in the background to stabilize the hydraulic conditions along the MI shear zone. (Photo © CFM Consortium 2015).