2.10. The development of a disposal facility usually involves an extensive programme of research, design and assessment work that may last for several years or decades. Once established, a disposal facility may be operated for several more decades. The lifetime of a radioactive waste disposal facility may be defined in three periods: the pre-operational period, the operational period and the post-closure period: @@- Activities commonly undertaken during the pre-operational period include the development of the disposal concept and the safety strategy, site evaluation (selection, verification and confirmation), environmental impact assessment5, initial design studies for the facility, the development of plans for research and development and monitoring, and the development of the detailed facility design. Licensing and construction of the facility also take place in this period.@@- The operational period begins when waste is first received at the facility and continues up to the final closure of all parts of the facility. Radiation exposures may occur in this period as a result of waste management activities and these are, therefore, subject to regulatory control in accordance with requirements for radiation protection and safety of workers. Safety assessment, monitoring, and research and development programmes should be used to inform management decisions on the operation and closure of the facility. During the operational period, construction activities may take place at the same time as waste emplacement in and closure of other parts of the facility. @@- The post-closure period begins after the facility is closed. After closure, a period of institutional control may contribute to the safety of certain disposal facilities (in particular, near surface disposal facilities). Institutional controls may be of an active or passive nature. Examples of active measures are the monitoring of radionuclide concentrations in environmental media or the monitoring of the performance and integrity of barriers, in particular in the case of near surface disposal facilities. Post -closure maintenance measures (e.g. the repair of covers for near surface disposal) also fall into this category. Other institutional controls may be of a passive nature. These could, for example, be ensuring that records on the disposal facility are kept and restrictions on land use are in place. States may have specific requirements for a maximum duration for which credit can be taken in the safety case for such controls. Since the functioning of such controls cannot be guaranteed, such controls cannot solely be relied on to ensure safety. They may, nevertheless, provide an important element of defence in depth.@@5) The 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. @@ (2) 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 radiation protection and safety. Monitoring, surveillance and testing programmes continue to inform operational management decisions and to provide the basis for decisions concerning the closure of the facility or parts of it. The safety case and safety assessments for the period of operation and for the period after closure are updated as necessary to reflect actual experience and increasing knowledge. During the operational period, construction activities may take place at the same time as waste emplacement in some parts of the facility and closure of other parts of the facility. This period may include activities for waste retrieval prior to closure (if retrieval is considered necessary), activities following the completion of waste emplacement, and closure.@@ (3) 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 closure, the safety of the disposal facility is provided for by passive means inherent in the characteristics of the site and the facility and in the waste package characteristics, although institutional controls, including some post-closure monitoring, may continue, for example, for the purposes of providing public assurance. The licence will be terminated when all the necessary technical, legal and financial requirements have been fulfilled.