Geological Disposal Concepts
Safe Disposal and its Repository for HLW and TRU Waste
The nuclear fuel cycle and types of radioactive waste for disposal by NUMO
NUMO is responsible for the geological disposal of vitrified high-level radioactive waste from the reprocessing of spent fuel used in the nuclear power plants, as well as TRU waste containing more than a specified concentration of long-lived radionuclides, which is generated by the operation and dismantling of reprocessing plants and MOX fuel fabrication plants.
Waste disposal method
Although radioactivity decays spontaneously with time, HLW and TRU remain radioactive for very long time periods and therefore it is necessary to isolate the waste from the human environment for this time. Different methods for disposing of the waste have been investigated by international institutions and countries worldwide, and the international consensus is that geological disposal in a stable host rock deep underground is the most safe and reliable method.
In Japan, it has been decided that the waste will be disposed of in stable host rock formation more than 300 meters underground. A multi-barrier system consisting of engineered and natural (geological) barriers will isolate and contain the radioactive waste over the long timescales.
Visual impression of a repository
The underground facilities will comprise tunnels for transporting and emplacing the waste packages and will be constructed in a stable host rock formation more than 300 meters underground.
On the surface, the facilities required for supporting underground excavation and operation and closure of the repository will be constructed.
Construction of the disposal tunnels, emplacement of the waste packages and backfilling of the disposal tunnels will be carried out underground. The underground facilities for a HLW repository are extensive and the various operations will be carried out in parallel in separate areas (disposal panels).
In the surface facilities, the vitrified HLW will be encapsulated in overpacks and the TRU waste will be packaged; the necessary inspections of the packages will also be conducted. These tasks will be carried out via remote operation in an area where radiation shielding is in place.
The facilities will also be designed against events such as earthquakes or fires and accidents where waste packages may fall or be overturned.
Example of repository layout
Example of co-located geological disposal facilities for HLW and TRU waste.
Scale of facilities
- Underground facilities:
- HLW disposal area:around 3km by 2km
TRU waste disposal area:around 0.5km by 0.3km