How long intermediate storages?
Extending current industrial storage facilities
View of the E/EV/SE storage facility for vitrified high-level waste at La Hague. Its current capacity is 4320 packages of vitrified CSD-V waste (2 modules of 180 shafts, each with a capacity of 12 CSD-V). It could be made up to eight times bigger by building extra modules. In addition to this storage capacity it has the R7 and T7 vitrification facilities, which can currently hold 12,420 packages. In total the capacity could be increased to nearly 50,000 CSD-V by building the planned extensions.
AREVAStorage is a means of modifying the way radioactive waste packages are managed over time, mainly by allowing the non-reprocessed spent fuel and the vitrified waste packages to cool down. This is the solution currently being used for the most highly radioactive waste, until a disposal facility is built. But could this role continue for periods of more than a century? The possibility of a storage facility lasting longer than a hundred years has not been proven, and consequently this cannot be guaranteed.
In 1991, when the Bataille Act on radioactive waste was passed, the alternatives were either to renew existing industrial facilities at the end of their life, or to decide immediately to deal with storage periods of several centuries by building storage facilities designed to last that long. A middle way was defined in 1998. This consisted of studying the durability of the most recent industrial storage facilities and issuing recommendations if it was felt that extending their life was appropriate.
When they were designed, the storage facilities currently in operation were scheduled to operate for only around fifty years. They are likely to have to accommodate all the primary packages of reprocessing waste from the current reactor fleet. Experience with operating these facilities has shown that they could be used for storage for up to a hundred years.
Research into the durability of reinforced concrete at high temperatures. With storage facilities designed to last for several centuries, the strength of the unprotected structural reinforced concrete would undoubtedly be one of the first problems to arise after a hundred years. CEA says it is confident that this type of concrete could last for up to 300 years, but in the CNE's opinion this has not been proven. In particular, the durability of the structure has not been proven if temporary overheating occurred during a loss of ventilation or a fire.
CEAWhen they were designed, the storage facilities currently in operation were scheduled to operate for only around fifty years. They are likely to have to accommodate all the primary packages of reprocessing waste from the current reactor fleet. Experience with operating these facilities has shown that they could be used for storage for up to a hundred years.
Research into the storage of packages of current reprocessing waste by extending the life of recent industrial storage facilities suggests that this type of storage would be safe for periods of around a century. Only the block diagrams and preliminary designs have been produced for new types of facility that can store waste for up to 300 years. To move beyond the preliminary design stage, a potential storage site would have to be selected. The choice of site is crucial for subsurface facilities, particularly to check the compatibility of the host rock with the storage facility being designed (compatibility of the water percolating through the rock with the concrete, thermomechanical effects, hygrometry, etc.).
Cross-sectional view of the compacted waste storage facility at La Hague: The storage area consists of four levels around 2m high, separated by concrete floors. Each of these levels has 20 cells separated by a central aisle. France's National Assessment Board (CNE) believes that these intermediate-level (ILW-LL) waste packages are ultimate waste which could be put into a geological disposal repository as soon as one is available. The storage of these packages is technically justified only by the absence of such a repository.
AREVA/Clefs CEAThe CNE's conclusions
According to the French National Evaluation Commission (the CNE
), 'long-term storage is chiefly a matter of engineering. Regardless of which option is chosen, it cannot be used for periods of more than a century without constant monitoring, maintenance and protection. Periodic operations to upgrade the facilities would become increasingly difficult with longer and longer storage periods. We are a long way from storage without the need for careful monitoring.'
The outcome of research into the surface or subsurface storage of waste, with the intention of retrieving that waste, depends on the envisaged storage period. If it is less than a century, which is enough to allow the current high-level long-lived waste to cool down, industrial storage facilities exist at La Hague and could be extended. The same goes for ILW-LL waste. If it is longer (e.g. 300 years) the issue needs to be taken into account of the durability of the storage structures to be built. No acceptable solution to this has yet been found.
The CNE adds: Without wishing to prejudge social stability in the long term, long-term storage places a heavy burden on future generations, which will also have to decide the ultimate fate of the waste.
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