Auvergne‑Rhône‑Alpes CERN accelerators and research centre Following the signing of an international agreement between France, Switzerland and the European Organisation for Nuclear Research (CERN) on 15 November 2010, ASNR and the Swiss Federal Office of Public Health (OFSP) – the Swiss radiation protection oversight body – are contributing to the verification of the safety and radiation protection requirements applied by CERN, including with regard to nuclear waste management and RST. CERN is not directly subject to Swiss or French regulations, but it must implement the best practices with regard to international regulations, standards and recommendations. Two joint visits by the Swiss and French authorities took place in 2025, focusing on access systems to areas where there is a risk of radiological exposure and on emergency management, including an emergency response exercise. These inspections found the practices to be satisfactory. SITES UNDERGOING DECOMMISSIONING Superphénix reactor and fuel storage facility The Superphénix fast neutron reactor (BNI 91), a 1,200 MWe sodiumcooled industrial prototype, is situated at Creys-Mépieu in the Isère département. It was definitively shut down in 1997. The reactor has been unloaded and the majority of the sodium has been neutralised and conditioned in concrete blocks. Superphénix is associated with another BNI, the Apec fuel storage facility (BNI 141). The Apec essentially comprises a pool containing the fuel unloaded from the reactor pressure vessel and the area for storing the soda concrete packages resulting from neutralisation of the sodium from Superphénix. In 2018, ASN authorised commencement of the second Superphénix decommissioning phase, which consists in opening the reactor pressure vessel to dismantle its internal components. In 2025, the licensee decommissioned the “small rotating plug” in the reactor vessel and in February transferred its “base-frame”, a massive activated part that is particularly irradiating, in a remote-controlled cutting workshop. However, due to technical difficulties, the licensee was unable to dispose of the parts cut from the base-frame to the Iceda facility. Following the removal of the base-frame, the reactor vessel has been completely drained and the licensee is preparing to decommission the safety vessel that surrounds the reactor vessel. In parallel with these operations on the reactor vessel and its internal equipment, the licensee also continued to decommission the equipment for the four steam generators, and at the end of the year carried out work to reprocess a hydrocarbon spill near the old engine room. In December 2025, EDF sent ASNR the Apec periodic safety review concluding report, and the report on the Superphénix reactor is due in March 2026. With regard to Apec, ASNR is attentive to the consistency between Apec’s operating deadline, set for 2035 by the Decree of 24 July 1985, and EDF’s strategy for managing stored fuel, some of whose deadlines exceed this timeframe. EDF will need to specify the prospects it envisages in this area. In December 2025, EDF also submitted a file to ASNR to update the site’s discharge permits. In view of the inspections conducted in 2025, ASNR considers that the safety and radiation protection of the Superphénix reactor decommissioning operations and of operation of the fuel storage facility is ensured satisfactorily. Tricastin Operational Hot Unit The Tricastin Operational Hot unit (BCOT) constitutes BNI 157. Operated by EDF, it was intended for the maintenance and storage of equipment and tooling, fuel elements excluded, originating from contaminated systems and equipment of the nuclear power reactors. The BCOT is situated at Orano’s Tricastin site. In a letter dated 22 June 2017, EDF declared final shutdown of the BCOT in June 2020 and its decommissioning was authorised by Decree 2023‑1049 of 16 November 2023. On completion of decommissioning, planned for 31 December 2033 at the latest, the cleaned-out buildings shall be returned to Orano. In 2025, EDF completed the decommissioning of the last rod control cluster guide tube containers and began electromechanical decommissioning of the equipment still present in the facilities, in particular the two glove boxes and the bunker 18 pool. In parallel with this decommissioning work, the licensee carried out a complete renovation of the site’s fire detection system in 2025, and plans to install a new ventilation system at the beginning of 2026 in order to adapt the installation to the work to come. ASNR considers that the BCOT decommissioning operations are being carried out under satisfactory safety and radiation protection conditions. ASNR actions to prevent radon risk Oversight actions In 2025, ASNR carried out three inspections of regional authorities responsible for educational establishments and day-care centres for children under the age of six (the municipalities of Givors and Montluçon, and the Auvergne-Rhône-Alpes Regional Council). ASNR also conducted four dedicated inspections of establishments with designated radon-risk workplaces (three thermal establishments and a hydroelectric dam). The results of these inspections show that the radon risk is being taken into account to varying degrees. While some establishments have implemented a satisfactory radon risk prevention approach, others have only partially taken into account the regulatory provisions relating to radon risk management.. Awareness-raising actions ASNR’s Lyon division also carries out awareness-raising initiatives about the risk of exposure to radon gas. In 2025, this included contributing to the awareness campaigns conducted by occupational health and prevention services in the Auvergne-Rhône-Alpes region as part of its participation in the working group on radon risk prevention under the Regional Occupational Health Plan (PRST). Areas with radon potential in mainland France, and particularly in the Auvergne-Rhône-Alpes region, are shown on page 99. 86 Rn radon ABSTRACTS – ASNR Report on the state of nuclear safety and radiation protection in France in 2025 45
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