1.5. Differing kinds of monitoring activities are necessary in each period in the lifetime of a radioactive waste disposal facility. This Safety Guide covers monitoring and surveillance in the pre-operational, operational, closure and post-closure periods for specific landfill disposal facilities, near surface disposal facilities, geological disposal facilities and disposal facilities for waste from thorium and uranium mining. The pre-operational, operational and post-closure periods set out in Ref. [2] can be further described as follows:
- The pre-operational period includes concept definition, site evaluation (selection, verification and confirmation), safety assessment and design studies. In the case of waste from mining, the pre-operational period corresponds to preparation for environmental remediation of mining facilities, tailings management facilities, piles of waste rock and clean-up waste of the contaminated sites (remediation of mining waste can be looked upon as disposal of the mining waste). The pre-remediation activities include environmental impact assessment1 of the sites surrounding the mine, selection and design of the remedial actions and implementation of an environmental monitoring programme that comprises monitoring of the impact of the remedial actions at the site and monitoring for any change in the environmental baseline conditions outside the remediation site. The pre-operational period also includes the development of programmes and procedures required in support of the application for a licence for construction and initial operation of a disposal facility. The monitoring and testing programmes that are needed to establish baseline conditions should be put in place during this period.
1) The term ‘environmental impact assessment’ is used here in a broad sense. In some States, the term denotes 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.
- The operational period begins when waste is first received at the facility. From this time, radiation exposures may occur as a result of waste management activities, and these are subject to control in accordance with the requirements for protection and safety. Safety assessments and the safety case for the period of operation are updated as necessary to reflect actual experience and increasing knowledge, gained both on the site and at other facilities, in the State and in other States. In the operational period, construction activities may take place at the same time as waste emplacement in and closure or decommissioning of other parts of the facility. This period may include activities for waste retrieval, if considered necessary, prior to closure, activities following the completion of waste emplacement and final closure, including backfilling and sealing of the facility. Records of the waste inventory should be kept throughout the operational period.
- Many reasons could lead to a decision to close a disposal facility. For example, the capacity of the disposal facility may have been reached; other solutions for disposal may have been found; or a political decision may have been made to close the facility. Irrespective of the rationale behind the decision, except in the case of remediation, a decision to close a disposal facility is also a decision to initiate a period of active institutional control, for a near surface disposal facility, or, for other disposal facilities, the post-closure period. Such a decision is specific to disposal facilities and is of high importance for near surface disposal facilities. Initiation of a period of active institutional control will lead to decisions on further activities following the completion of waste emplacement, namely closure and sealing of the disposal facility. At this time, the duration of this period of active institutional period should be determined in accordance with a ‘de minimis’ approach to the risks incurred by a potential human intruder.
- The post-closure period begins at the time when all the engineered containment and isolation features have been put in place, operational buildings and supporting services have been decommissioned, and the facility is in its final configuration. After its closure, the safety of the disposal facility is provided for by means of passive features inherent in the characteristics of the site and the facility and characteristics of the waste packages. A monitoring and surveillance programme is put in place aimed at confirming that the disposal system is performing as expected. Monitoring may also be carried out to enhance confidence in, and therefore acceptance of, the disposal process. For near surface disposal facilities in particular, institutional controls are put in place to prevent intrusion into the facility. Depending on national legislation, the licence to operate a disposal facility may be terminated after the period of active institutional control when all the necessary technical, legal and financial requirements have been fulfilled.