4.25. A graded approach is required to be taken in determining the scope, extent and level of detail of the safety case and supporting assessment (IAEA SSR-5[2], IAEA GSR Part 4 (2009)[3]). The graded approach adopted should be explained and justified, and should be such that the scope, extent and level of detail of the safety case and supporting assessment are commensurate with the level of risks posed by a facility or activity and the stage of facility development, e.g. generic disposal concepts being considered prior to site selection might be considered in less detail than for a specific site and disposal facility. Three aspects to be considered in a graded approach are given in Ref. [3]: the magnitude of the possible radiation risks and the maturity and complexity of the facility. Further guidance on the application of these criteria to waste disposal facilities is provided in paras 6.23?6.28.