Use of the Safety Case to Focus KMS Applications

The safety case, as defined in Japan, is an integrated set of arguments to show that a repository is sufficiently safe during both operational and post-closure phases. It explicitly includes the findings of a safety assessment and a demonstration of confidence in these findings. It is developed in a stepwise manner, with provisional cases used to support decisions at major project milestones. Social acceptance is acknowledged to be critical and hence a safety case includes not only technical components, but also the arguments required to explain fundamental issues to all key stakeholders. In the JAEA KMS project, the safety case has been found useful as a framework that allows all supporting R&D to be seen in the context of its applicability. Various tools have been examined to develop associated argumentation models and they have been seen to provide an overview that is valuable to both the users and producers of knowledge. The paper will review progress to date in this work, with illustrative examples of argumentation networks and an outline of future developments and challenges.