The Experiments presently running at the Grimsel Test Site
PHASE VI PROJECTS
Since 1984 the Grimsel Test Site has been carrying out a wide range of investigations in many fields, including geology, geophysics, hydrogeology, rock mechanics and radionuclide transport. The scientific work performed has been already shown to over 50,000 visitors and has been presented in many papers at conferences or published in scientific journals. Presently the existing projects are running under Phase VI (See here for full history of experiements ).
Three Phase V projects, FEBEX, HPF and GMT were officially extended into 2005. This allowed a greater volume of high quality data to be collected from these projects where long term monitoring is a fundemental part of the investigation.
In general, the Phase VI projects are focusing on :
- Development and optimisation of the technology, transporting, emplacing, quality-assuring, monitoring and, if required, retrieving of radioactive waste.
- Extending past studies of processes in the geosphere (mainly associated with radionuclide mobility) to more closely represent the physical scales (at least 10s of metres) and boundary conditions (e.g. low water velocities) relevant to repository environments. This requires multi-decade duration tests, more than an order of magnitude longer than has been the case in any rock laboratory anywhere in the world to date.
- Monitoring and extending the knowledge and experience available from the present generation of radioactive waste experts by training the next generation who will actually build repositories.
Overview of Phase VI Experiments presently running at the Grimsel Test Site
The following projects are presently running at the Grisel Test Site. Full details are available following the links.
CFM - Colloid Formation and Migration
The CFM experiment looks at the role played by colloid () generation rates and mechanisms at the Engineered Barrier System (EBS) – host rock boundary under in-situ conditions. The formation and transport of colloids and colloid-associated radionuclides is monitored under repository relevant flow conditions and over relevant distances.
FEBEXe - Full-scale Engineered Barriers Experiment
The initial aim of the FEBEX experiment, back in 1997, was to study the behaviour of the nearfield components (Engineered Barrier System, host rock) for a high-level radioactive waste repository in crystalline rock. Detailed understanding of early time coupled processes is needed to predict the nearfield evolution in terms of evolution of thermal conductivity of partially saturated buffer, the role of thermal convection, the on-set of corrosion/gas production, gas transport capacity of the nearfield (saturation history) and the geochemical evolution of the nearfield (e.g. iron/bentonite interactions).
FEBEXe - during construction, and computer model of the HLW disposal concept
FORGE - Laboratory Column Experiments
The FORGE experiment aims, under realistic boundary conditions, to obtain larger scale (decimetre scale) 2-phase flow properties for host rock and EBS materials, to assess and visualise gas and water flow in sand/bentonite mixtures and to demonstrate the functioning of gas permeable plugs and seals on a decimetre scale.
Figure 1: Drawing of the mock-up experiment with the steel cylinder confining the experiment, mortar discs at moth ends (grey/brown), the S/B seal (brown/yellow), the pure bentonite (yellow) and the ring-TDRs (black). Instruments are schematically indicated to show the locations of the monitoring levels.
LCS - Long-term Cement Studies
The overall aim of the LCS project is to increase the understanding of high-pH cement interaction effects in the repository near field and the geosphere in order to make confident, robust and safety-relevant predictions of future system behaviour, irrespective of repository host rock, engineered barrier system (EBS) and waste type. This requires an improved thermodynamic database and a refinement of existing modelling tools
Long Term Cement Studies (LCS) Concept
LTD - Long Term Diffusion
This is a long-term, large-scale experiment which aims to further examine in-situ matrix diffusion and pore space visualisation at the Grimsel Test Site
long Term Diffusion concept
NF-PRO - Near Field Processes
A vital aspect of Nagra's involvement is, beside the further monitoring of water content changes in the bentonite buffer, the refinement of the TDR technique as a method for water content measurements in low porosity rock formations. Since 1996, the TDR probes are monitoring the evolution of the EBS system. The laboratory experiment will feed into the ongoing FEBEX long-term monitoring programme at the GTS by providing new calibration functions for the granite probes. Post-processing of the entire TDR data base will provide an updated TDR data set for the FEBEX master data base
PSG - Pore Space Geometry
This is an in-situ resin impregnation experiment which aims to visualise connective porosity and open pore spaces available for matrix diffusion in intact rock matrices.
GAST - Gas-Permeable Seal Test
The production of gas will occur during the life of the Engineered Barrier System (EBS). The GAST test looks at the effective functioning of gas permeable seals at realistic scale and with realistic boundary conditions, the validation and, if necessary, improvement of current conceptual models for the re saturation and gas invasion processes into S/B seals.
Schematic picture of the GAST experiment layout with the 8-10m long sand/bentonite plug in between two gravel packs.
ESDRED - Test and Evlauation of Monitoring Systems
The full-scale low-pH shotcrete plug was constructed in 2007 in the context of ESDRED and the TEM project has been part of the experiment set-up right from the start. While the overall goals are to demonstrate the construction feasibility and to test the support capacity of the plug, the objectives of the TEM project are to investigate the efficiency of an existing wireless magneto-inductive (MI) transmission technique and to evaluate seismic tomography as a non-intrusive monitoring technique.
Perspective view of the experimental layout and monitoring installations
C-FRS - CRIEPI's Fractured Rock Studies
The aim of CRIEPI’s in-situ experiments at the GTS is to demonstrate the performance of newly developed technologies for fracture characterisation and tracer testing. The relevant parameters of the investigations are fracture aperture and geometry.
Japanese research teams and GTS staff at the C-FRS site. Photo: comet.