5.1. As indicated in para. 4.44, assessment of the post-closure radiological impact forms the core of the safety case for a disposal facility. Radiological impact assessment for the period after closure is a process of evaluating the performance of a disposal system and quantifying its potential impact on human health and the environment. The assessment includes both quantification of the overall level of performance of the disposal system and analysis of the associated uncertainties. The methodology used for radiological impact assessment should be systematic and the assessment should adequately address all safety relevant aspects in a graded manner (see para. 5.6).