Retrievability

In this context, retrieval means bringing back to the earth's surface the copper canisters containing the spent nuclear fuel from the repository in the bedrock.

Taking into Account the Retrievability Option

The purpose of final disposal is to permanently isolate the spent nuclear fuel from organic nature in such a way that no supervision is required once the repository is sealed. However, it is possible to retrieve the spent nuclear fuel if adequate technical and financial resources are available to do so.

Reasons for Retrievability

Retrievability offers future generations an opportunity to assess the solution in the light of any future knowledge at the time. It is possible that a technology is developed in the future whereby spent nuclear fuel can be transmuted harmless or utilised economically. The basic assumption is that retrieving will not become necessary due to safety reasons.

Final Disposal Is the Least Risky Alternative

According to current thinking, the disposal of spent fuel in a repository is less risky than storing spent fuel in an interim storage. Since final disposal is scheduled to start in Finland in 2020, it is natural that the possibilities of technological advances during this and the following decade are taken into account in preparations and planning.

Methods Required for Retrieving

The retrieving will use the same regular work methods that were used in the excavation and construction of the repository. Work for developing methods is also in progress: SKB in Sweden, for example, is currently investigating new methods. Posiva works in cooperation with SKB which means that the results can also be utilised in Finland.

Retrievability at Different Stages of Final Disposal

Retrieving is possible at every stage of final disposal. It is easiest at the stage where the canister hole has not yet been sealed off because the bentonite surrounding the canister has not expanded to press tightly against the canister yet. The canister can be removed from the hole using the canister handling system of the canister transport vehicle and then transported back to the encapsulation plant above ground.

If the repository has already been sealed off, the necessary infrastructure has to be constructed and the tunnels excavated open before retrieving the canisters, much in the same manner as when the facilities were originally constructed. At that time, the bentonite has already expanded and is pressed tightly around the canisters, which means that it has to be loosened before removing the canister.  Saline water of high concentration is used for loosening. The saline water pressure injected into the bentonite transforms it into slurry that can be removed by pumping. After that, the canister can be lifted from its hole using the canister handling system of the transport vehicle. The canister is designed to be strong enough to endure lifting and transportation, even after long periods.