LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 4 – Oversight of the Flamanville EPR reactor The EPR is a 1,600 MWe PWR using a design that contains a number of changes by comparison with that of the reactors currently in operation in France. It meets reinforced safety objectives: reduction in the frequency of incidents or accidents, limitation of discharges, reduced volume and activity of waste, reduced individual and collective doses received by workers (in normal operating and incident situations), reduced overall frequency of core melt, taking account of all types of failures and hazards, and reduced radiological consequences of accidents, in particular in the event of core melt. The Government authorised the construction of an EPR-type reactor on the Flamanville site (already equipped with two 1,300 MWe reactors) through Decree 2007-534 of 10 April 2007, following a favourable opinion issued by ASN at the end of its investigation. In a resolution of 7 May 2024, ASN authorised commissioning of the Flamanville EPR reactor. This authorisation allowed EDF to load nuclear fuel into the reactor vessel in May 2024 and carry out start-up tests, followed by operation of the reactor. The authorisation issued by ASN is accompanied by technical specifications that govern, in particular, the performance and monitoring of start-up tests after the nuclear fuel has been loaded into the reactor. These requirements stipulate that divergence and increases beyond 25% and 80% of rated power are subject to authorisation by ASN. EDF then began start-up tests with the loaded core and operation of the reactor. In particular, EDF carried out the first divergence of the reactor in September 2024, followed by the first connection to the electricity grid in December 2024. In 2025, EDF continued the start-up test programme, notably testing the reactor core at 25% of its rated power. In the light of the results of these tests and the satisfactory operation of the core monitoring and protection systems, ASNR gave its agreement, in a resolution dated 31 January 2025, to continuing start-up tests at a higher power level. EDF then carried out «major transients» (loss of external power supply test, manual reactor shutdown, turbine trip and islanding) and core tests at various power levels, up to 80% of rated power. ASNR considers these start-up tests to be satisfactory. In a decision dated 12 December 2025, ASNR gave its approval for start-up tests to continue beyond 80% of the reactor’s rated power. A detailed assessment of the operation of the Flamanville EPR in 2025 is provided in the regional overview for the Normandy region (see page 73). International Operational Experience Feedback ASNR takes part in the forum of authorities overseeing the safety of EPR reactors around the world. It meets regularly with the Finnish, Chinese and British nuclear safety authorities to benefit from their experience. ASNR closely examines the OEF from reactors operating in other countries and regularly verifies that the lessons learned are taken into account by EDF. A specific inspection in 2025 examined the organisation implemented by EDF to act on OEF from other EPRs: ASNR notes that EDF maintains an important link with its counterparts and thus benefits from their feedback. 5 – Regulation and oversight of the EPR 2 reactors project EDF has started a programme to build EPR 2 type reactors in France. A first pair of reactors is planned for the Penly site in the Seine-Maritime département, a second on the Gravelines site in the Nord département and a third on the Bugey site in the Ain département. For the Penly site, a public debate was held from 27 October 2022 to 27 February 2023, following which at the end of June 2023, EDF submitted a creation authorisation application for two BNIs to the Minister responsible for nuclear safety. The preparatory works necessary for the siting of the reactors were authorised by a Decree of 3 June 2024. The construction of the nuclear island may only begin after the Creation Authorisation Decree for the BNIs has been issued. For the Gravelines and Bugey sites, a public debate was held from 17 September 2024 to 17 January 2025 and from 28 January to 15 May 2025 respectively. 5.1 EPR 2 reactors safety options The EPR 2 is a new PWR model with an output of around 1,670 MWe, which aims to incorporate operating experience feedback from the design, construction and commissioning of the EPR reactors, as well as experience feedback from the operation of the existing EDF reactors. In the same way as the EPR reactors, it aims to meet the general safety objectives for third-generation reactors. Furthermore, this reactor will integrate all the lessons learned from the Fukushima Daiichi NPP accident, as of the design stage. This more specifically entails reinforcing the design against external natural hazards and consolidating the independence of the installation and the site in an accident situation until such time as the resources can intervene. HIGHLIGHT No. 14 First outage for refuelling of the Flamanville EPR reactor EDF plans to begin the first refuelling outage of the Flamanville EPR in early autumn 2026. During this outage, as well as renewing the fuel, EDF will be carrying out maintenance and testing operations on its installations. It will also carry out the first complete requalification of the main primary cooling system which will include a hydrostatic pressure test. These numerous checks are important operations to verify that the equipment is in good condition after the reactor’s first operating cycle. EDF will be modifying certain parts of its installations during this outage. In particular, it will replace the heat exchangers between the intermediate cooling system and the essential service water system, which were undersized when the reactor was designed, as well as the vessel head, which is affected by a manufacturing anomaly. EDF will also carry out activities that were not carried out before the reactor started up, such as the stress relieving heat treatment of several secondary system welds. Lastly, a large number of nuclear pressure equipment inspections will reach their regulatory deadlines at the same time, creating a peak workload for EDF and the inspection bodies. EDF has asked ASNR to postpone certain activities so that they can be finetuned over subsequent outages. This will avoid load peaks during reactor operation. ASNR is currently examining the authorisation applications for modifications that EDF wishes to make. It will also check the measures taken by EDF to prepare and schedule the activities to be carried out during the outage. ASNR Report on the state of nuclear safety and radiation protection in France in 2025 307 01 05 02 06 03 07 04 08 09 10 11 13 12 A / Z
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