3.9. The following requirement applies for all facilities and activities, including disposal facilities: “It shall be determined in the assessment of defence in depth whether adequate provisions have been made at each of the levels of defence in depth” (Requirement 13, Ref. [3]). This requirement is further explained by the following statement: @@- “It has to be determined in the safety assessment whether adequate defence in depth has been provided, as appropriate, through a combination of several layers of protection (i.e. physical barriers, systems to protect the barriers, and administrative procedures) that would have to fail or to be bypassed before there could be any consequences for people or the environment” (para. 4.12 of Ref. [3]).