The GAST section has been updated with new sections and images from recent events. Click to view
Press Release :
Testing a gas-permeable seal for deep geological repositories
Guttannen (Bern) – A multi-year, large-scale demonstration experiment has started at Nagra’s Grimsel Test Site, with the aim of confirming important aspects of the functioning of tunnel seals in future geological repositories. The experiment seal consists of a clay (bentonite)/sand mixture and will be used to demonstrate the feasibility of controlled gas transport from a radioactive waste repository on a realistic scale.
Nagra began operating the Grimsel Test Site, an underground rock laboratory located at an altitude of 1730 metres in the Swiss Alps, 28 years ago. Numerous experiments have already been carried out on the construction and safe operation of future geological repositories for radioactive waste. A new milestone in the history of the Grimsel Test Site was reached in May: the completion of the construction and the start of the operation of the GAST (Gas-Permeable Seal Test) experiment, which investigates the emplacement and behaviour of the seals (barrier) for future geological repositories.
The focus of this experiment is the transport of water during the saturation period and the transport of gas through such barriers. The experiment will bring the current state of knowledge in this area one step forward. The seal consists of a mixture of sand and clay that has been specially developed over the last 10 years. Depending on the proportion of clay in the mixture and the density of the material, the desired properties – very low water permeability and a high transport capacity for gases – can be reached in an optimum way.
Installation of the measurement instrumentation for the GAST experiment at the Grimsel Test Site (© Comet Photoshopping)
“On the 10th of May, we installed the final component of the experiment, namely the concrete plug with a diameter of 4 metres and a thickness of 2 metres” explains Joerg Rueedi, Nagra’s project manager for the GAST experiment. The concrete plug should be capable of withstanding a water pressure of up to 50 bars and will allow testing of the seal under simulated hydraulic conditions that would correspond to a repository at a depth of 500 metres.
Metal framework with the cabling for the measurement instrumentation for the GAST experiment (© Comet Photoshopping)
The GAST experiment is co-financed by Nagra’s sister organisations in France (ANDRA) and South Korea (KRMC) and is planned to run till the end of 2015. A series of laboratory experiments is being performed in parallel with the field experiment. “The experiment will verify a key component of a future geological repository”, says Joerg Rueedi.
Contact person: Stratis Vomvoris, Head of Nagra’s ISP Division: telephone (+41) 56 437 13 24