5.7. "The safety case has to be developed progressively and elaborated as the project proceeds” [1] to provide a basis for licensing applications at key steps in the development of the geological disposal facility (see Fig. 1). The regulatory body may require an update of, or revision to, the safety case prior to making a decision on proceeding to the next step in the development and operation of the geological disposal facility. The formality and level of technical detail of the safety case will depend on the stage of development of the project, the decision in hand, the audience to which it is addressed and specific national requirements.