GTS Information

Around 300 million years ago, granitic melts solidified at a depth of around 10 - 13 km. The volume of the rock decreased due to cooling and deep fracture systems formed. Residual magma rose through these to form dyke rocks (lamprophyres and aplites).

The rocks of the Aar Massif remained virtually undisturbed for more than 200 million years. Extensive deformation of the rock body then began during the course of the alpine orogeny, around 40 million years ago. The Aar Massif subsided and was overlain by the alpine nappes moving towards the north.

At the time of maximum overburden (approximately 12 km), the rock was exposed to high temperatures (around 450°C) and pressures (around 300 MPa). The main schistosity and shear zones were formed during this period.

The crystalline rock in the Grimsel area has long been thought of as a "Massif", a large block of crystalline basement pushed up through the overlying sediments. However, recent observations in the new Lötschberg railway tunnel indicate that it is, in fact, a massive thrust sheet, overlying sediments in some areas.

In the uplift phase - still continuing with a rate of around 0.5 to 0.8 mm per year today - the tension joints with their beautiful crystals (see The Crystal Cave) were formed around 16 million years ago.

Full-Scale Emplacement (FE) Experiment, Nagra participation in the EU project
Large Underground Concept Experiments (LUCOEX)

Invitation
to the presentation of the FE backfilling machine
on Monday 19th of May 2014 starting at 3pm and
to dinner in the evening, followed
by a one-day workshop on
bentonite material production & emplacement
on Tuesday 20th of May 2014
from 9am until approx. 4pm.

Location
The presentation and workshop will be
held in the facilities of Belloli SA
in Grono GR, Switzerland
(https://goo.gl/maps/jeU9K).

Please don't hesitate to contact Ms. Fankhauser (+41 56 4371 339 This email address is being protected from spambots. You need JavaScript enabled to view it.) if you have any further questions or require assistance.

We would be pleased to welcome you in Grono!
Herwig R. Müller (Nagra), PM of the FE experiment
Hanspeter Weber (Nagra), LUCOEX work-package leader

Supporting Documentation
                      
 

Bentonite Block Pedestal Load Tests carried out at the Grimsel Test Site

A multi-barrier approach ensures the long-term isolation of radioactive waste and is the adopted solution of preference for radioactive waste management. The Engineered Barrier System (EBS) is one part of this passive multi-barrier system approach and it refers to all barriers introduced through technological (engineered) activities. It is complemented by the natural barrier, also referred to as the geological barrier or geosphere.

Most of the experiments running at Grimsel are focusing on using in-situ tests to analyse and characterise the near field of a nuclear waste repository. The near field includes the Engineered Barrier System (EBS) and the immediate rock surrounding a repository. In Nagra's concept, the disposal tunnels and caverns are placed deep underground (from around 600m) and in stable rock formations. Slightly different disposal methods are envisaged for the high level waste (HLW - spent fuel rods from reactors or vitrified waste) and the intermediate to low level waste (I/LLW - industrial waste). These two concepts are explained below.

Nagra's concept for an underground nuclear waste repository

1. High level waste (HLW) tunnels

The high level waste is contained within large steel disposal canisters.

These canister are placed on bentonite pedestals within the disposal tunnel at regular intervals, and the tunnel backfilled with bentonite.

Nagra's high level waste (HLW) disposal concept - cutaway

Video overview of disposal concept for High Level Waste (HLW)

2. Low level waste (LLW) caverns

Low level waste is contained within steel drums, and these steel drums are placed into concrete disposal casks, and filled with mortar.

The disposal casks are stacked into the low level waste disposal caverns which are lined with concrete. When full, the caverns are backfilled with mortar.

 Nagra's low level waste disposal cavern concept - cutaway

Nagra's low level waste disposal cavern concept - cutaway - close-up

The low level waste (LLW) disposal cavern is shown below during the operational phase, and when it has been backfilled with mortar and sealed.

Nagra's low level waste (LLW) disposal concept - operational

Nagra's low level waste (LLW) disposal concept - backfilled

Video overview of disposal concept for High Level Waste (HLW)

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

 View the main CFM section

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.

CFM concept layout - click for a larger image

FEBEXe - Full-scale Engineered Barriers Experiment

 View the main FEBEXe section

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

 View the main FORGE section

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

 View the main LCS section

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

 View the main LTD section

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

 View the main NF-PRO section

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

PSG - Pore Space Geometry

 View the main PSG section

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

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

GAST - Gas-Permeable Seal Test

 View the main GAST section

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

 View the main ESDRED section

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

 View the main C-FRS section

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.