Druck Version: Nagra Nationale Genossenschaft für die Lagerung radioaktiver Abfälle Seite: 83420 Datum & Zeit: 21.05.2012 20:22:46 Sprache: EN

Geological repository for low- and intermediate-level waste

The Nuclear Energy Act specifies that low- and intermediate-level waste has to be disposed of in a deep geological repository. The facility will have caverns capable of accommodating a volume of around 100 000 cubic metres of packaged waste.

A vertical shaft or a tunnel will provide access to the disposal caverns, located at a depth of 300 to 500 metres. The caverns can be completely backfilled after several decades. Once the main repository has been closed, the behaviour of the safety barriers can continue to be monitored in the pilot facility.
Schema Tiefenlager SMA
  1. Main facility L/ILW
  2. Pilot facility
  3. Test zones
  4. Access tunnel
  5. Ventilation shaft and construction shaft
The surface infrastructure of a geological repository consists of a surface facility with access road and, if possible, a rail link; there are also shaft installations whose locations will be decided at a later stage.

The surface facility serves as the portal to the repository. The waste is delivered here and prepared for emplacement. The facility includes an administration building, a visitors centre, an encapsulation plant and various operations buildings, as well as the access to the repository.

The area required for the surface facility is around 5 hectares, with a width of 130 metres (guide values). The exact location and the layout of the buildings are decided by the public and the authorities together with Nagra. The facility can be modified to fit with its surroundings, for example it could be located in an industrial zone near a population centre, at the edge of a forest and protected from view or on the site of a gravel-pit, partly hidden by sloping terrain or in the open landscape.

Other components of the surface infrastructure include the shafts for ventilation and material transport. The shaft heads and associated small structures are located above the repository and require an area of around one hectare. Disposal areas are required for the material that will be excavated during construction of the access tunnel and the disposal galleries. Some of this material can be re-used later for closing the repository.

Once the waste has been emplaced, the repository will be monitored for several decades. In this phase, part of the surface infrastructure will no longer be required and will be demolished. Later, once the monitoring period is over, the remaining buildings will be demolished, with the exception of installations for long-term monitoring and marking.

Surface facility for a low- and intermediate level waste repository

Model of a site-specific layout for the surface facility of a deep repository for low- and intermediate-level waste. The location, layout and integration into the landscape will be decided together with the regional population. (Image: maars, Zürich)

Modell der Oberflächenanlage SMA
Model of the surface facility for the L/ILW repository
  1. L/ILW encapsulation plant
  2. Treatment plant for operational waste and garages
  3. Processing plant for backfilling and sealing materials
  4. Fire service building
  5. Electrical installations building
  6. Ventilation plant
  7. Access to the repository
  8. Workshop
  9. Visitors centre
  10. Administration centre
  11. Train lock/delivery terminal
  12. Vehicle lock

The repository for low- and intermediate-level waste (L/ILW) consists of a test area with a rock laboratory, a pilot facility and a main facility with large disposal caverns. These installations are located at a depth of around 400 metres and are linked to the surface by an access tunnel and a shaft.

 

Once the ramp and the shaft have been excavated, the first step will be to construct the rock laboratory. Here, the host rock at the disposal site will be investigated in detail for a period of around five years.

 

The pilot facility is a smaller disposal cavern in which the first waste containers will be emplaced. These will be monitored during the entire operational and monitoring phase.

 

The main repository consists of several large disposal caverns in which the L/ILW is stacked in concrete containers.

 

The tunnels and caverns are equipped with a rail system and cranes to allow the emplacement process to be carried out remotely.

 

Depending on the particular conditions at the site, it may be possible to construct some of the operational and waste reception facilities beneath the surface.

The drums with the conditioned low- and intermediate-level waste are delivered to the surface facility of the repository preferably by rail.

After an entry control, the drums are transported to the transfer station where they are checked and then loaded into prefabricated disposal containers made of concrete. These are filled with cement mortar.

The containers are transported via the access tunnel to the disposal caverns using the tunnel railway. From there, the containers are transferred to their emplacement position using a travelling crane and are stacked on top of one another.

 

The caverns are backfilled stepwise with a special mortar and later sealed.

The repository for low- and intermediate-level waste has four different safety barriers - three engineered and one geological.

 

The waste is solidified in a matrix and enclosed in drums (first engineered barrier).

 

Several of these drums are placed in a concrete container which is filled with mortar (second engineered barrier).

 

The concrete containers are stacked on top of and adjacent to one another in large caverns and the spaces between the containers are backfilled with a special mortar (third engineered barrier).

 

Together with the overlying formations, the host rock forms the geological barrier.

SMABarrieren_2337

Model of a disposal container for low- and intermediate-level waste. (image: Nagra)