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

Focusing on : How colloids affect the transport of radionuclides in the host rock boundary of the Engineered barrier System.

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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.

A picture
CFM concept layout - click for a larger image

 

FEBEXe - Full-scale Engineered Barriers Experiment

Focusing on : The early evolution of bentonite within the Engineered Barrier System.

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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 Concept - construction view
FEBEXe - during construction, and computer model of the HLW disposal concept

 

FORGE - Laboratory Column Experiments

Focusing on : The properties of the host rock and Engineered Barrier System materials with resepct to gas and water flow and the functioning of the gas permeable plugs and seals.

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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.

 

3D Drawing of the FORGE mock-up experiment at Grimsel

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

Focusing on : The interaction effects of high-ph cement on the near field.

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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

LCS Concept
Long Term Cement Studies (LCS) Concept

 

LTD - Long Term Diffusion

Focusing on : Demonstration of in situ radionuclide retardation within the rock matrix, with verification used for testing existing modelling codes.

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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

Experimental concept - Log Term Diffusion project
long Term Diffusion concept

 

NF-PRO - Near Field Processes

Focusing on : Development and refinement of new Time Domain Reflectometry (TDR) probes for crystalline rock.

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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

Experimental Setup
Experimental Setup

 

PSG - Pore Space Geometry

Focusing on : investigatng the pore spaces and matrix diffusion, which affect the transport of radionuclides through the near field rock.

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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.

 
PSG animation
alt Drilling of injection borehole.
alt Drilling of observation boreholes
alt Resin injection
alt Polymerisation of resin
alt Overcoring - removal of core.

 

 

GAST - Gas-Permeable Seal Test

Focusing on : construction and testing of in-situ gas permeable seals.

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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.

alt
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

Focusing on : istallation and testing of new wireless monitoring equipment and seismic tomogrophy in a real environment.

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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

Focusing on : testing new technology for fracture characterisation and tracer testing.

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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.

CRIEPI’s Fractured Rock Studies - Staff
Japanese research teams and GTS staff at the C-FRS site. Photo: comet.

 

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.