6.1. The development of a geological disposal facility can take decades. The goal of assessing safety at key decision points in the development process, prior to commitment of additional resources, makes it practical to divide the programme into a series of steps. Typical steps should be set at regulatory or governmental decision points for the approval of construction of a geological disposal facility (construction), the approval to receive and emplace waste (operations) and the approval to close the facility permanently (closure). At each of these steps, the safety case is required to be updated [1]. Such an approach provides multiple opportunities to assess the quality of the technical programme and the safety case supporting the decision making process and thus provides confidence in these. Confidence in the safety and feasibility of a geological disposal facility is enhanced through the step by step process and by the maturing safety studies as the project progresses. Figure 1 illustrates a development timeline for a disposal facility, including specification of decision points and phases of activities.