Grimsel Test Site (Switzerland)

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FEBEX-DP Full-scale Engineered Barrier Experiment – Dismantling Project

Spanish Flag  CIEMAT, Spain
Swedish Flag  Swedish Nuclear Fuel and Wast Management Co. (SKB), Sweden
Finnish Flag  POSIVA, Finland
Finnish Flag  Korea Atomic Energy Research Institute (KAERI), KOREA
Swiss Flag  Nagra, Switzerland
Japanese Flag  Obayashi, Japan
USA Flag  USDOE/LBNL, USA
UK Flag  RWM, UK
German Flag  BGR, Germany
French Flag  ANDRA, France
Czech Flag  SURAO, Czech Republic

FEBEX-DP Overview Video

 

History

The FEBEX experiment consists of an in-situ full-scale engineered barrier system (EBS) test for the disposal of high level waste (HLW). It is performed under natural conditions in crystalline rock in which the canisters are placed horizontally in drifts and are surrounded by a clay barrier constructed of highly compacted bentonite blocks. It was initiated and led by Enresa in 1995 and has been one of the research subjects in three subsequent European projects. In 2008, a consortium consisting of SKB, Ciemat, Posiva, and Nagra (and since 2013 KAERI) undertook the continuation of the experiment under the project name FEBEXe.

 

Heating started in 1997 and since then a constant temperature of 100°C has been maintained in the remaining heater, while the bentonite buffer has been slowly hydrating in a natural way. A total of 632 sensors in the bentonite barrier, the rock mass, the heaters and the service zone record temperature, water saturation, humidity, total pressure, displacement, and water pressure. A partial dismantling and sampling of the EBS was carried out during 2002.

At the end of the heating phase, the hydration pattern is relatively symmetric, with no major differences along the axis. Although the host rock is characterized by heterogeneities with zones of higher permeability, the resaturation process is driven by the suction of the bentonite rather than by the availability of water in the rock, especially in the early phase. After 18 years, the water content in the buffer close to the heater still continues to increase slowly. The hydraulic pore pressures in the buffer and the geosphere have practically stabilized. The total pressure in general continues to increase in most points into the buffer, where in some parts pressures of over 6 MPa are registered.

The long monitoring phase and the partial dismantling in 2002 indicate that the EBS has largely performed as expected. Furthermore, the major processes and couplings affecting the buffer saturation during the initial thermal period identified prior to the start of the experiment have been confirmed (Lanyon & Gaus, 2013).

FEBEX-DP

For the dismantling of the second heater, the project FEBEX-DP was initiated and will last until the end of 2016. Additional partners were invited to join the FEBEX-DP project with ANDRA, BGR, Obayashi, RWM, SURAO, US-DOE/LBNL following this invitation.

1. Febex tunnel in Grimsel.
2. Drilling of small pilot boreholes.
3. Planning and drilling of larger boreholes
4. Overcoring of plug/bentonite interface
5. Removal of overcore
6. Dismantling first stage of Plug
7. Planning of further boreholes
8. Dismantling second stage of Plug
9. Planned Removal of dummy heater
10. Removal of dummy heater
10a. Main heater exposed, ready for extraction
10b. Removal trolley arrives
10c. Removal trolley positioned, pulley attached
10d. Extraction of heater
10e. Trolley removes heater
11. Planned removal during dismantling
12. Fully dismantled tunnel

The objectives of the FEBEX-DP are:

  • Characterization of the key physical properties (e.g., density, water content) of the barrier and their distribution and comparison with results from the partial dismantling and model predictions
  • Characterization of corrosion and microbiological processes on heater, instruments and coupons resulting from evolving redox conditions and saturation states, including gas analysis 
  • Characterization of mineralogical interactions at material interfaces (e.g., cement-bentonite or iron-bentonite, rock-bentonite) by macro- and micro level studies 
  • Assessment of sensor performance 
  • Further increasing understanding of the thermo-hydro-mechanical (THM) and thermo-hydro-chemical (THC) processes through integration of monitoring and dismantling results

The dismantling activities started in late 2014 and were completed during the summer of 2015. An extensive laboratory programme on the over 1300 samples is being undertaken.

For more information please contact : This email address is being protected from spambots. You need JavaScript enabled to view it. or This email address is being protected from spambots. You need JavaScript enabled to view it.

References

Lanyon G.W., Gaus I. (Ed.) (2013): Main outcomes and review of the FEBEX In Situ Test (GTS) and Mock-Up after 15 years of operation. Nagra Arbeitsbericht. NAB 13-096. Nagra, Wettingen.

excavation section 36
Section 36 during excavation (May 2015)

Full Scale Engineered Barriers Experiment - Dismantling Project (FEBEX-DP)

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.