I.1.
Siting is a fundamentally important activity in the geological disposal of radioactive waste. In the siting process for a radioactive waste disposal facility, four stages may be recognized: (i) a conceptual and planning stage; (ii) an area survey stage, leading to the selection of one or more sites for more detailed consideration; (iii) a site investigation stage of detailed site specific studies and site characterization and (iv) a site confirmation stage. In site selection, one or more preferred candidate sites are selected after the investigation of a large region, the rejection of unsuitable sites and the screening and comparison of the remaining sites. From several, possibly many, prospective sites identified at the start of a siting process, a selection is made of one or more preferred sites on the basis of geological setting and with account taken of other factors. Sociopolitical factors are an important consideration in any site selection process (e.g. demographic conditions, transport infrastructure, existing land use). Decision making in the site selection process may involve various levels of involvement of the public and local communities, including the use of veto and volunteerism. The national preferences expressed will vary from State to State and hence cannot be addressed within international guidance for the safety of geological disposal facilities. During the initial stages of site selection, geological and hydrogeological site specific information may be sparse or lacking. Nevertheless, such data that are available and expert judgement should be used in support of a decision to select one or more locations as a prospective underground disposal site. A promising site should display evidence of favourable natural containment and isolation characteristics for the waste types under consideration and should provide indications that all necessary engineered barriers to prevent or retard the movement of radionuclides from the disposal system to the accessible environment can be implemented. This evidence needs to be tested in subsequent detailed site investigation, characterization and associated safety assessment modelling.
I.2.
Detailed site investigation and characterization span the final stages of a siting process (stages iii and iv) and Section 6 of this Safety Guide provides recommendations particularly for the detailed site characterization stage leading to site confirmation. This Appendix provides a brief overview of some important points concerning the conceptual and planning stage, the area survey stage and the site investigation stage. This is followed by further guidance on the types of data expected from an investigation and characterization programme.