In accordance with the general principles of radiation protection, the dosimetric impact of the site on the workers and public after delicensing must be as low as reasonably possible (ALARA principle(1)). ASN is not in favour of introducing generalised thresholds and considers it preferable to adopt an optimisation approach, based on technical and economic criteria, according to the future usages of the site (confirmed, planned and practicable). Nevertheless, whatever the case, once the site has been delicensed, the induced radiological exposure must not exceed the statutory value prescribed in the Public Health Code of 1 millisievert (mSv) over one year for all the usage scenarios. The doctrine implemented by ASN is set out in the guides relative to the structure clean-up operations (Guide No. 14, available at asn.fr), and the management of polluted soils in nuclear installations (Guide No. 24, available at asn.fr). The provisions of these guides have already been implemented on numerous installations with varied characteristics, such as research reactors, laboratories, fuel manufacturing plants, etc. 1. ALARA principle (As Low As Reasonably Achievable). 1.3 Decommissioning regulatory framework Once a BNI is definitively shut down, it must be decommissioned. Its purpose therefore has to change with respect to that for which its creation was authorised, as 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 on the basis of an opinion from ASN. This decree sets out, among other things, the main decommissioning steps, the planned decommissioning end date and the final state to be achieved. As part of its oversight duties, ASN monitors the implementation of the decommissioning operations as directed by the decommissioning decree. In order to avoid fragmentation of the decommissioning projects and to 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 PHASES IN THE LIFE OF A BASIC NUCLEAR INSTALLATION At least two years before the planned shutdown date, the licensee must inform the Minister responsible for nuclear safety and ASN of its intention to definitively shut down its facility. This notification is made public. The licensee must submit the decommissioning file to the Minister 2 years at the most after shutdown notification. This file sets out the decommissioning operations projected by the licensee and the measures it will take to limit the impacts on people and the environment. 2 years maximum Transmission of the decommissioning file Shutdown notification As of the date of final shutdown, the licensee is no longer authorised to operate its facility. The license starts to prepare for the decommissioning of its facility. The decommissioning preparation operations often consist in removing the radioactive and chemical substances present in the facility (spent fuel), reorganising the premises (to create storage areas) or adapting the utility networks (ventilation, electrical power distribution). Final shutdown END OF OPERATION DECOMMISSIONING PREPARATION PHASE 338 ASN Report on the state of nuclear safety and radiation protection in France in 2022 • 13 • Decommissioning of Basic Nuclear Installations 13
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