LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT In 2025, the public inquiries were held for the fourth periodic safety reviews of Gravelines NPP reactors 2 and 4 and reactor 1 at the Chinon NPP. The fifth periodic safety review In 2023, EDF sent ASN the envisaged guidelines for the generic phase study programme for the fifth periodic safety review of the 900 MWe reactors. In the light of the major modifications made during the fourth periodic safety reviews, which will continue up until 2036 for the last reactor, EDF intends to focus the fifth periodic safety review: ∙on verifying the conformity of the installations with their applicable requirements, maintaining equipment qualification and managing ageing, for operation up to 60 years; ∙on reassessing the management of risks and detrimental effects, anticipating the effects of climate change (external hazards, water resource, etc.) – see Highlight No. 12. After consulting the public and further to the opinion of the Advisory Committee of Experts for Nuclear Reactors (GPR) ASN issued a position statement in December 2024 on these guidelines. This periodic safety review serves to determine the conditions for continued operation of the reactors beyond 50 years. ASNR considers that the general guidelines adopted by EDF for this review are pertinent and consistent with the current level of knowledge. This fifth periodic safety review should allow consolidation of the major safety improvements made to the reactors during their fourth periodic safety review and reinforce the way in which the effects of climate change are addressed. However, ASNR asks EDF to supplement or clarify some of these general objectives. 3.3.2 – The 1,300 MWe reactors The third periodic safety review At the beginning of 2015, ASN issued a position statement on the generic aspects of the continued operation of the 1,300 MWe reactors beyond thirty years of operation. On this occasion, ASN underlined the importance of the modifications made by EDF following their third periodic safety review. Within the framework of this review, EDF is notably deploying material and operational modifications in order to mitigate the consequences of an SG tube break accident, to prevent the occurrence of severe accidents with early loss of containment, and to reduce the risk of uncovering the fuel assemblies present in the spent fuel pool. With regard to hazards, EDF is modifying its installations in order to guarantee operation of the equipment needed for the safety of these reactors in the event of a heatwave, to protect the safety-important equipment against projectiles created by strong winds and to prevent the risks of explosion further to an earthquake. To help conclude the generic phase of this review, ASN issued additional requests in 2021 applicable to all the 1,300 MWe reactors, with the aim of reinforcing their safety. The third ten-yearly outages for the 1,300 MWe reactors were completed in 2025. The fourth periodic safety review In July 2017, EDF sent ASN the guidelines it envisaged for the generic phase of the fourth periodic safety review of the 1,300 MWe reactors. In 2019, ASN issued a position statement on these guidelines, after involving the public and consulting the GPR: ASN considered that the general objectives set by EDF for this review were acceptable in principle. Similarly to those adopted for the fourth periodic safety review of the 900 MWe reactors, these objectives aim to demonstrate that in the event of a design basis accident it would not be necessary to implement population protection measures and that, in the event of a severe accident, only population protection measures that are limited in space and time would be required. With regard to the safety of the spent fuel pool, ASN asked EDF to set an objective of no uncovering of the assemblies and to eventually return the installation to and permanently maintain it in a state without pool water boiling. The modifications associated with this periodic safety review will also incorporate those linked to deployment of the “hardened safety core”. In 2024, ASN continued with the examinations performed for the generic phase of this periodic safety review. ASN convened its GPEs on four occasions with respect to hazards, accidents without core melt, severe accidents and the in-service strength of the reactor vessels and changes to the calculation methods used to justify the mechanical strength of the equipment of the MPS and MSS. Based on the conclusions of this expert appraisal, ASNR issued a position statement in July 2025 on the generic phase of this periodic safety review, after consulting the public and obtaining the opinion of the Advisory Committee of Experts for Nuclear Reactors (GPR – see the Highlight on this topic in the introduction to this report). EDF will begin the first ten-yearly outage associated with this periodic safety review at the beginning of 2026. 3.3.3 – The 1,450 MWe reactors The third periodic safety review After consulting the public and obtaining the opinion of the GPR, ASN issued a position statement in July 2023 regarding the guidelines envisaged by EDF for its study programme of the generic phase of the third periodic safety review of the 1,450 MWe reactors. The periodic safety review will allow definition of the conditions for continued operation of these reactors for up to 40 years. ASN considered that the general objectives set by EDF for this review were acceptable in principle. These objectives are consistent with those set for the fourth periodic safety reviews of the 900 MWe and 1,300 MWe reactors. ASN asked EDF to add to or clarify some of these general objectives, in the same way as it had done for the 900 MWe and 1,300 MWe reactors. The safety reassessment of these reactors and the resulting improvements will be carried out in the light of the safety objectives of the new-generation reactors, such as the EPR, the design of which meets significantly reinforced safety requirements. In addition, the modifications associated with this periodic safety review will incorporate those linked to deployment of the “hardened safety core”. In 2025, ASNR started the examinations performed for the generic phase of this periodic safety review. ASNR will issue a position statement for this generic phase in early 2029. HIGHLIGHT No. 13 Fourth periodic safety review of 1,300 MWe reactors: expert assessments backed by a vast programme of studies and research conducted by IRSN Between 2019 and 2024, as part of the fourth periodic safety review of 1,300 MWe reactors, experts from IRSN (now ASNR) produced more than 40 technical reviews and four reports for the Advisory Committee of Experts for Nuclear Reactors (GPR). These assessments were based on the conclusions of numerous studies carried out in-house, in particular using calculation tools developed within the institute. These calculation tools capitalise on several years’ experience and knowledge gained from specific experimental programmes. For example, the scientific calculation tool TENPO (for TENue des POrtes – Door resistance) was developed by IRSN specialists responsible for understanding the physical phenomena associated with fires inside buildings. This tool is an expert system for assessing the relevance of the measures adopted by licensees to limit the consequences of fires inside buildings. Similarly, over 60 Probabilistic Safety Assessments (PSAs) have been carried out using models developed specifically in-house. Lastly, IRSN experts have been able to draw on the knowledge acquired in the course of numerous international experimental programmes in which ASNR is a partner. For example, the ROSAU (Reduction of Severe Accident Uncertainties) programme, operating under the aegis of the OECD and supported by 15 partners from eight countries, has advanced our understanding of the physical phenomena of interaction between corium and concrete following a core meltdown accident that led to the breaching of the reactor vessel. 306 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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