6.4. The first step in the development of a disposal facility addresses concept definition. The safety case for this step should present the strategy for safety and the way it will be met. At this stage, it will generally not be possible to provide a detailed description and assessment of the facility. Nevertheless, some initial information, for example, on the type of host rock, may be available. Key aspects relating to the strategy for safety and to the conceptual design of the facility should be addressed. In the absence of any quantitative demonstration, qualitative justification for the strategy for safety adopted will have to be provided in the safety case. In addition, the approach to safety assessment, the management system and management of uncertainties should be set out and explained, even though these aspects will evolve significantly in subsequent steps of the project.