6.57. Post-closure performance of a geological disposal facility should be considered in the initial design and in subsequent updates to the safety case. Prior to regulatory approval for facility closure, the safety case should be updated to provide sufficient evidence that the closure system will be effective and that the safety of the geological disposal facility after closure will be in accordance with regulatory requirements. The effectiveness of the closure system could be shown by demonstrating an understanding of the natural evolution of the site, by in situ testing, by data analysis and modelling and by the use of suitable natural analogues.