Chinon site Situated in the municipality of Avoine in the Indre‑et‑Loire département, on the left bank of the river Loire, the Chinon site accommodates various nuclear installations, some in operation, others undergoing decommissioning. On the south side of the site, the Chinon B NPP comprises four in-service reactors of 900 MWe; the first two commissioned in 1982 and 1983 constitute BNI 107, while the second two commissioned in 1986 and 1987 constitute BNI 132. To the north, the three old graphite-moderated GCRs designated Chinon A1, A2 and A3, are currently being decommissioned. The site also accommodates the Irradiated Materials Facility (AMI), currently being decommissioned, whose former expert assessment activities have been entirely transferred to a new laboratory called the “Lidec” and to Inter-Regional Fresh Fuel Warehouse (MIR). 1. Among the possible scenarios for decommissioning the highly activated or contaminated structures, we find decommissioning “in air” and decommissioning “under water”. In the case of the GCRs, the “under water” approach consists in filling the reactor core (reactor pressure vessel) with water in order to benefit from the protective effect of a layer of water with respect to the radiation-related risks, but it is more complicated to implement than the “in air” approach. In view of the major technical difficulties (sealing of the reactor pressure vessel and treatment of the contaminated water), but also the technological advances bringing other solutions, such as remote operation, EDF has finally adoptyed the decommissioning “in air” scenario, which overcomes the problems linked to the use of water. CHINON NUCLEAR POWER PLANT Reactors B1, B2, B3 and B4 in operation ASN considers that the performance of the Chinon NPP stands out positively with regard to safety and is in line with the general assessment of EDF in the areas of radiation protection and the environment. The progress noted in 2022 in the area of safety was consolidated in 2023. With regard to safety, ASN observes that operational management performance has remained satisfactory in a particularly busy industrial context, with periods of simultaneous outages of several reactors. A number of events nevertheless revealed a lack of rigour on the part of the workers or in the organisation and distribution of roles within the operational management teams. These situations rapidly led to corrective actions, the effectiveness of which must be monitored over time. As far as maintenance of the installations is concerned, the site’s performance remains satisfactory. A few areas for improvement emerge nevertheless, notably in activity preparation and worker monitoring. The year 2023 was marked by the fourth ten-yearly outage of reactor 1, during which substantial maintenance operations were carried out, including the replacement of two sections of the primary cooling system. ASN considers that the radiation protection performance of the Chinon NPP remains in line with the average for the EDF plants. Nevertheless, the performance is variable, with a worker contamination level that is among the lowest of EDF, but persistent shortcomings in industrial radiography work. ASN considers that the areas for progress identified for 2023 concerning industrial radiography work and effective application of the chosen prevention measures with regard to radiation protection and radiological work regimes remain applicable for 2024. The environmental protection performance of the Chinon NPP is stable. ASN considers that the NPP manages its discharges and the containment of hazardous liquid substances proficiently. However, the management of waste, and waste removal in particular, must be improved. 2024 must be used to eliminate the waste resulting from reactor maintenance which has been accumulating on the site for several years. With regard to labour inspections and in view of the inspections conducted in 2023, ASN considers that the Chinon NPP must take better account of the electrical and ATEX risks, whether in the exhaustiveness of the checks or the correction of the anomalies detected. Furthermore, although the absence of any serious accidents is to be underlined, ASN considers that the site must make further progress in accident prevention, particularly in the activity preparation phase. Lastly, the site’s responsiveness regarding its exchanges with the labour inspectors is to be underlined. Reactors A1, A2 and A3 undergoing decommissioning The graphite-moderated GCR series comprises six reactors, including Chinon A1, A2 and A3. These first-generation reactors used natural uranium as the fuel, graphite as the moderator and were cooled by gas. This plant series includes “integrated” reactors, whose heat exchangers are situated under the reactor core inside the vessel, and “non-integrated” reactors, whose heat exchangers are situated on either side of the reactor vessel. The Chinon A1, A2 and A3 reactors are “non-integrated” GCRs. They were shut down in 1973, 1985 and 1990 respectively. Reactors A1 and A2 were partially decommissioned and transformed into storage facilities for their own equipment (Chinon A1 D and Chinon A2 D). These operations were authorised by the Decrees of 11 October 1982 and 7 February 1991 respectively. Chinon A1 D is partially decommissioned at present and has been set up as a museum – the Museum of the Atom - since 1986. Chinon A2 D is also partially decommissioned and, until the end of 2022, housed GIE Intra (robots and machines for interventions on accident-stricken nuclear installations). Complete decommissioning of the Chinon A3 reactor was authorised by the Decree of 18 May 2010, with a decommissioning “under water” scenario. In March 2016, EDF announced a complete change of decommissioning strategy for its definitively shut down reactors. In this new strategy, the planned decommissioning scenario for all the reactor pressure vessels involves decommissioning “in air”(1) and the Chinon A2 reactor pressure vessel would be decommissioned first (see chapter 14 of the full ASN Report). In this context, ASN has analysed the periodic safety review concluding reports submitted by EDF concerning the six GCRs, 50 ABSTRACTS – ASN Report on the state of nuclear safety and radiation protection in France in 2023 Regional overview of nuclear safety and radiation protection • CENTRE-VAL DE LOIRE •
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