Safety requirements for the decommissioning of nuclear facilities

The main safety requirements for protection of workers, the public and the environment during all stages of decommissioning as set down in the international safety standards [41] emphasise the importance of considering both radiological and non-radiological hazards in an integrated manner. Decommissioning activities are considered to be part of the original prac­tice, and the safety requirements of the Basic Safety Standards [38] apply to all decommissioning activities.

It is important that a safety culture is fostered and maintained in both the operating organisation and that individuals responsible for decommis­sioning activities are trained to appropriate levels of awareness of health, safety and environmental matters. Safety needs to be maintained during the entire decommissioning process and beyond if a facility is to be in compli­ance with the site release criteria [43]. As with pre-disposal and disposal, the safety requirements for decommissioning apply to governments, opera­tor organisations and the regulatory body.

The national legal framework for decommissioning needs to include provisions for the use, possession, storage and handling of all radioactive material generated during decommissioning.

All phases of decommissioning, from the initial plan to the final release of the facility from regulatory control, must be regulated. The regulatory body responsible for all phases of decommissioning must establish the safety standards and requirements for decommissioning, and carry out activities to ensure that the regulatory requirements are met.

The operating organisation is responsible for all aspects of safety and environmental protection during the decommissioning activities and must provide financial assurances and resources to cover the costs associated with safe decommissioning, including management of the resulting radio­active waste.

The operating organisation is also required to define a decommissioning strategy consistent with national decommissioning and waste management policy. The preferred decommissioning strategy is immediate dismantling; however, if another practical strategy is selected it needs to be based on evaluation of factors such as: the availability of waste disposal or long-term storage capacity for decommissioning waste; the availability of a trained workforce; the availability of funds; co-location of other facilities on the same site requiring decommissioning; technical feasibility; and optimisation of the radiation protection of workers, the public and the environment. The strategy must be justified and it must be demonstrated that in the future no undue burdens will be imposed on future generations.

It is important that the strategy includes provisions to ensure that, if final shutdown occurs earlier than expected, the facility shall be brought to a safe configuration and a decommissioning plan is in place for approval and implementation.

It is essential that appropriate means are available to manage waste (including pre-disposal and disposal) of all categories [3] in a timely manner, with account taken of the overall decommissioning strategy. This involves the application of the concept of clearance [44] of material resulting from decommissioning activities, i. e. material or items released from regulatory control. For sites with more than one facility, a global decommissioning programme needs to be developed for the entire site that ensures interde­pendences are taken into account in the planning for individual facilities.

It is important that the operating organisation prepares and maintains a decommissioning plan throughout the lifetime of the facility (from the design stage to termination of activities) that shows that the decommission­ing can be accomplished safely to meet the defined end state. For existing facilities where a decommissioning plan does not yet exist, a suitable plan for decommissioning needs to be prepared as soon as possible.

The decommissioning plan has to be supported by an appropriate safety assessment covering the planned decommissioning activities and any abnor­mal events that may occur during decommissioning. The assessment must address occupational exposure and potential releases of radioactive ma­terial with resulting exposure of the public.

A graded approach needs to be applied to development of the decommis­sioning plan commensurate with the type and extent of hazards. The initial plan must be reviewed and updated periodically, at least every five years or as prescribed by the regulatory body, or when specific circumstances warrant, such as if changes in an operational process lead to significant changes to the plan. The plan must address all relevant safety aspects (see [45-47]) such as carrying out a baseline survey of the site, retaining key staff and ensuring that institutional knowledge about the facility is maintained.

Prior to the implementation phase of decommissioning (about 2 years), a final decommissioning plan must be prepared and submitted to the regula­tory body for approval. Interested parties have to be provided with an opportunity to review the final decommissioning plan and to provide com­ments on the plan to the regulatory body prior to its approval.

National legislation must set out the responsibilities with respect to finan­cial provisions for decommissioning (e. g., mechanism for adequate financial resources for safe and timely decommissioning). It is very important that adequate finances for safe decommissioning, including the management of the resulting waste, are available when needed, even in the event of prema­ture shutdown of the facility, and financial assurances to provide for the required resources have to be in place before authorisation to operate the facility is given. If financial assurance for the decommissioning of an exist­ing facility has not yet been obtained, suitable funding provision needs to be put in place as soon as possible. Provision for financial assurance is required prior to licence renewal or extension.

Where the decommissioned facility is released with restrictions on its future use, financial assurance adequate to ensure that all necessary controls remain effective have also to be obtained before authorisation is terminated by the regulatory body.

An organisation for the management and implementation of decommis­sioning has to be established as part of the operating organisation, with the responsibility for ensuring that decommissioning will be conducted safely. Regardless of the type of organisational arrangements, the ultimate respon­sibility for safety remains with the operating organisation, although it is permissible to delegate the performance of specific tasks to a subcontractor. The operator must ensure that individuals responsible for performing activ­ities during the decommissioning process have the necessary skills, expertise and training to complete the decommissioning process safely. This must be in line with a comprehensive quality assurance programme under the oper­ating organisation’s management system [48] and be applied to all phases of decommissioning. It is important that the management of the decommis­sioning project is tailored to the project’s complexity and size and to the associated potential hazards.

The operating organisation must implement the decommissioning and related waste management activities in compliance with the national safety standards and requirements. The operating organisation must also inform the regulatory body prior to shutting down the facility permanently and the implementation of the decommissioning plan can only start after regulatory approval is issued.

In the case of deferred dismantling, the operating organisation has to ensure that the facility has been placed, and will be maintained, in a safe configuration and will be appropriately decommissioned in the future. To provide an adequate level of safety, the operating organisation must, inter alia, prepare and implement appropriate safety procedures; apply good engineering practice; ensure that staff are properly trained and qualified and are competent; and keep and submit records and reports as required by the regulatory body.

Decontamination and dismantling techniques must be chosen such that the protection of workers, the public and the environment is optimised and the hazards and the generation of waste are minimised.

It is important that prior to using any new or untried decommissioning methods, the use of such methods must be justified and addressed within an optimisation analysis supporting the decommissioning plan. Such analyses must be subject to review and approval by the regulatory body.

Emergency planning arrangements, commensurate with the hazards, need to be established and maintained and incidents significant to safety reported to the regulatory body in a timely manner. A proper waste man­agement path for all waste streams arising from decommissioning activities must also be provided.

Upon completion of decommissioning, it must be demonstrated that the end state criteria as defined in the decommissioning plan and any additional regulatory requirements have been met. The operating organisation can only be relieved of further responsibility for the facility after approval by the regulatory body [43].

A final decommissioning report must be prepared that records, in par­ticular, the end state of the facility or site, and this report must be submitted to the regulatory body for review. In this respect, a system must be estab­lished to ensure that all records are maintained in accordance with the records retention requirements of the quality assurance system and the regulatory requirements. If waste remains stored on the site after decom­missioning, a revised or new, separate authorisation, including requirements for decommissioning, must be issued for the facility. If a facility cannot be released for unrestricted use, appropriate controls need to be maintained to ensure protection of human health and the environment. These controls must be specified and approved by the regulatory body.

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