ASN Report 2018

Pursuant to the provisions of Article 8.3.2 of the Order of 7 February 2012, “ the final state reached on completion of decommissioning must be such that it prevents the risks or adverse effects that the site may represent for the interests mentioned in Article L. 593-1 of the Environment Code, in view of the projections for reuse of the site or buildings and the best post-operational clean- out and decommissioning methods available under economically acceptable conditions ”. In this context, ASN recommends, in accordance with its decommissioning doctrine, that the licensees deploy decommissioning and clean-out practices taking into account the best scientific and technical knowledge available at the time and under economically acceptable conditions, with the aim of achieving a final status in which all the hazardous and radioactive substances have been removed from the BNI. This is the reference approach according to ASN. Should it be difficult to apply this approach due to the nature of the contamination, ASN considers that the licensee must go as far as reasonably possible in the clean-out process. Whatever the case, the licensee must provide technical or economic justification that the reference approach cannot be applied and that the clean-out operations cannot be taken further under acceptable economic conditions using the best technical clean-out and decommissioning methods available. In accordance with the general principles of radiation protection, the dosimetric impact of the site on the workers and public after decommissioning must be as low as reasonably possible. ASN therefore considers that the defining of thresholds is not reasonable. An exposure leading to an effective annual dose of 300 microsieverts for the public (i.e. one third of the annual dose limit of 1 millisievert for the public) is only acceptable after demonstrating the integration of an optimisation process, in accordance with the IAEA texts on the unconditional release of a site contaminated by radioactive substances. In 2016, ASN thus updated and published a technical guide on structure clean-out operations (Guide No. 14, available on asn.fr ) . The provisions of this Guide have already been implemented on numerous installations with diverse characteristics, such as research reactors, laboratories, fuel manufacturing plant, etc. ASN also published in 2016 a guide relative to the management of polluted soils at nuclear installations (Guide No. 24, available on asn.fr ). 1.3  ̶  Decommissioning regulatory framework Once a BNI is definitively shut down, it must be decommissioned and therefore the framework under which it is authorised must change since the Creation Authorisation Decree specifies the operating conditions of the installation. Furthermore, the decommissioning operations imply a change in the risks presented by the installation. Consequently, these operations cannot be carried out within the framework set by the Creation Authorisation Decree. The decommissioning of a nuclear installation is prescribed by a new decree issued after consultation with ASN. This decree sets out, among other things, the main decommissioning steps, the decommissioning end date and the final state. In order to avoid fragmentation of the decommissioning projects and improve their overall consistency, the decommissioning file must explicitly describe all the planned operations, from final shutdown to attainment of the targeted final state and, for each step, describe the nature and scale of the risks presented by the facility as well as the envisaged means of managing them. This file is subject to a public inquiry. Given that installation decommissioning operations are often very long, the decommissioning decree can stipulate that some steps will be subject to prior approval by ASN on the basis of specific safety analysis files. The diagram above illustrates the corresponding regulatory procedure. The licensee must demonstrate in its decommissioning file that the decommissioning operations will be carried out in as short a time frame as possible. The decommissioning phase may be preceded by a preparatory stage, provided for in the initial operating licence. This preparatory phase allows for removal of a portion of the radioactive and chemical substances as well as preparation for the decommissioning operations (readying of premises, preparation of worksites, training of teams, etc.). It is also during this preparatory phase that installation characterisation operations can be carried out (production of radiological maps, collection of pertinent data (operating history) with a view to decommissioning, etc). For example, the fuel in a nuclear reactor can be removed during this phase. Phases in the life of a basic nuclear installation Shutdown notification Transmission of the decommissioning file 2 years minimum* 2 years minimum 3 years maximum * Delicensing Decommissioning Creation Authorisation Decree Decommissioning Decree** Operation of the BNI * Deadline extendable by 2 years in certain cases. ** The decommissioning decree takes effect on the date ASN approves the revision of the general operating rules and no later than one year after publication of the decree. Decommissioning preparation operations Final shutdown 338  ASN report on the state of nuclear safety and radiation protection in France in 2018 13 – DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS