The high-level waste packages requiring disposal will probably be the CDS-V vitrified waste containers currently produced at the La Hague plant. Packages arriving at the repository will initially be received in above-ground buildings, where they will be inspected and unloaded from their transport casks.
They will then be reinspected and placed in disposal packages. Before being transferred underground, disposal packages will be placed in casks to shield against radiation.
Each cask will be placed on a funicular and carried down an access ramp to the disposal facilities 500 m underground.
ANDRA video Route taken by HLW waste from reception to disposal cells
The surface areas of several square kilometres envisaged for planned repository sites can be accounted for by the need to separate the waste containers in a disposal cell (unlike ILW-LL waste, which can be stacked) and to space out the disposal cells.
Disposing of spent fuel assemblies, which release comparatively more heat than vitrified waste, would require even larger areas. Conversely, implementing advanced separation to extract caesium and strontium from the vitrified waste packages produced in La Hague would considerably increase the repository's capacity. These two fission products are the main sources of the heat released by waste during the critical initial period of around 100 years.
Waste will be disposed of on a single level located in the middle of the Callovo-Oxfordian layer in order to maximise the thickness of impermeable argillite above and below it. The disposal cells are blind tunnels that will be sealed when full. The access shafts will be grouped together on one side, and the filling areas as well as the general architecture of the disposal facilities will be based on a dead-end configuration. The disposal cells will be laid out so as to limit the temperature of the rock in contact with them to 100°C. Accordingly, the cells containing heat-releasing waste will have to be spaced out.