1Containment denotes all methods or physical structures designed to prevent or control the release and the dispersion of radioactive substances. Isolation of the waste from the accessible biosphere substantially reduces the likelihood of inadvertent human intrusion into the waste and its consequences.

2The concept of developing a safety case for disposal facilities, as outlined in this publication, is used in many States. The terminology used is different, though, in some States. For example, in the United States of America the term ‘total system performance analysis’ is used (together with the regulations relevant to the specific disposal method), covering all aspects of the safety case as described in this Safety Guide. In France, the term ‘dossier’ is used to describe the safety case. In Germany and Switzerland, the term ‘Sicherheitsnachweis’ is used. In Spain, the term ‘estudio de seguridad’ is used to describe the safety case.

3The United States Department of Energy, Waste Isolation Pilot Plant (WIPP), Carlsbad, NM, USA.

4Very short lived waste and exempt waste are not considered further in this Safety Guide because they do not require specialized radioactive waste disposal facilities.

5The term is used here in a broad sense. In some States, the term ‘environmental impact assessment’ is a specified process covering all potential impacts of the project with a view to soliciting acceptance of a project from all relevant authorities and which often involves participation of the public.

6The current edition of the International Basic Safety Standards is Ref. [19].

7It is recognized that radiation doses to individuals in the future, including those that may occur after institutional management of a waste disposal facility has ceased, can only be estimated. “Nevertheless, estimates of possible doses and risks for long time periods can be made and used as indicators for comparison with the safety criteria” (para. A.4 of Ref. [2]).

8Such demonstrability may be ensured by means of assessment, testing or other physical demonstration of functionality.

9A component of the disposal system may be considered robust if it will continue to fulfil its expected safety function(s) no matter what kind of perturbations may reasonably be expected to occur. The disposal system may be considered robust if it continues to provide adequate protection and safety under a wide range of conditions and scenarios that may reasonably be expected to occur.

10The term ‘site’ refers to the area of the former site and its environs, as in the future the boundary of the site will have little meaning.

11A moderately swelling clay found in the region of the town of Boom, Belgium.

12With regard to the use of collective doses in such assessments, the following statement from Ref. [21] should be taken into account: “Both the individual doses and the size of the exposed population become increasingly uncertain as the time increases. Furthermore, the current judgements about the relationship between dose and detriment may not be valid for future populations. ...[F]orecasts of collective dose over periods longer than several thousand years and forecasts of health detriment over periods longer than several hundred years should be examined critically.”

13The need for consistency does not preclude emphasizing different arguments depending on the audience, as people with different backgrounds may be convinced by different arguments.