5.1. A safety case is a collection of arguments and evidence that demonstrates that a particular facility, part of a facility or an activity on a site is safe. The safety case should be prepared for at least each major step in the development, operation and closure of a geological disposal facility and may include some or all of the submissions to the regulatory body seeking approval to proceed from one step to the next. The safety case is progressively enhanced as development, operation and closure are carried out, so that all safety related occurrences and the remedial actions taken are recorded, and that there is at all times an up to date set of documents that demonstrate that the facility is safe and is expected to remain safe over the long term. In this section, the terms ‘operational safety case’ and ‘post-closure safety case’ are used. In practice, these may be separate entities or parts of one overall safety case for the facility.