Stepwise decision making and options for retrieval in the Swedish KBS-3 concept

The long time aspect of radioactive waste management has resulted in the adoption in Sweden of an ethical principle that requires present generations to manage radioactive waste in a way that will not burden future generations, and at the same time avoid to unnecessarily hinder future generations to retrieve the waste or take actions to change the disposal system. The present Swedish repository design has been developed to get a high and provable safety and to get a robust repository. A consequence of this has been a high barrier integrity that gives the system a high retrievability. The development of a repository system is a step-wise process, as much of the information on repository performance will only become available as the steps are carried through. In such work, retrievability can be extended also to other steps in handling or conditioning, i.e. indicating a general ability to reverse any step taken. At each decision-step, the confidence in achieving a safe repository has to be balanced against the commitments the step involves. An important factor in this balance is the feasibility of stepping back in the process. Thus, reversibility/retrievability are valuable systems characteristics in decision-making under uncertainty. It is generally agreed that the retrievability option should not be used as an excuse for developing a repository with lower safety levels than otherwise would have been required. In fact, such an action is in practice equivalent to an intentional transfer of burdens to future generations. (author)