ASN Report 2020

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 shut down or undergoing decommissioning. On the south side of the site, the Chinon B NPP comprises four in-service 900 MWe reactors; the f irst two constituting BNI 107 were commissioned in 1982-1983, while the second two constituting BNI 132 were commissioned in 1986‑1987. To the north, the three old graphite-moderated Gas-Cooled Reactors (GCRs) designated Chinon A1, A2 and A3, are currently being decommissioned. The site also accommodates the Irradiated Materials Facility (AMI), designed for the expert assessment of activated or contaminated materials, whose activities have now ceased and been entirely transferred to a new laboratory called the Lidec, and to Inter-regional fresh fuel warehouse (MIR). Chinon nuclear power plant Reactors B1, B2, B3 and B4 in operation ASN considers that the performance of the Chinon NPP is in line with its general assessment of the EDF plants in the areas of nuclear safety, radiation protection and the environment. ASN considers that the site is maintaining a satisfactory standard in incident and accident management and in the analysis of deviations that could affect safety. The year 2020 was nonetheless marked by an increase in significant events linked to failure of the operating teams to comply with the general operating rules, which is why ASN considers that the safety performance of the NPP is dropping. The radiation protection performance of the Chinon NPP, which has been dropping since 2018, can be improved. The year 2020 was marked by a non-negligible number of significant radiation protection events, notably due to workers failing to wear dosimeters and to deficiencies in application of the radiation protection measures mentioned in the worksite risk analyses. The environmental performance of the Chinon NPP must be improved. Although the discharge limits for gaseous and liquid effluents are on the whole respected, a case of exceeding of the average activity concentration was observed in 2020 in the Loire further to an error in the activity analysis of an effluent discharged by the site. Furthermore, the times taken by the NPP to reconstitute the sealing of the network that is supposed to collect the fire extinguishing water in the event of a fire are inappropriate for the risks, and the rigour of waste management is not of the required level. The licensee must take priority actions to address these deviations. As far as labour inspection is concerned, the licensee must make improvements to ensure better control of the electrical risk and to respond to the findings made during the inspections in the buildings of the DUS sets commissioned in 2020. Lastly, an inspection was carried out on the secondment of foreign employees. In the context of the Covid‑19 pandemic, various inspections concerning management of the health crisis were carried out on documents and in the f ield. The observations addressed to the NPP and to the subcontractor companies resulted in corrective actions. Reactors A1, A2 and A3 undergoing decommissioning The graphite-moderated GCRs 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” GCR reactors. 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 author- ised 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 decom- missioned and houses GIE Intra (which operates robotised machines for interventions on accident-stricken nuclear instal- lations. Complete decommissioning of the Chinon A3 reactor was authorised by the Decree if 18 May 2010, with a decom- missioning “under water” scenario. In March 2016, EDF announced a complete change of decom­ missioning 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” and the Chinon A2 reactor pressure vessel would be decommissioned f irst (see chapter 13). ASN Chairman’s resolution CODEP-CLG-2020-021253 of 3 March 2020 requires EDF to submit a decommissioning f ile for the Chinon reactors A1 and A2 and to update that of Chinon A3 before the end of 2022 to take account of the changes in decom­ missioning scenario and time frame modifications. The decommissioning worksites were delayed by several months in 2020 on account of the restrictions laid down to combat the Covid‑19 pandemic. EDF has nevertheless put in place its activity continuity plan to maintain some of the worksites and perform the periodic inspections and tests of its equipment. With regard to the Chinon A2 reactor, EDF has continued the decommissioning preparation operations outside the reactor pressure vessel and carried out investigations inside the pressure vessel. EDF also continued the decommissioning of the Chinon A3 heat exchangers following several interruptions in 2019 and 2020 due to the discovery of asbestos. ASN considers that the level of safety of the Chinon nuclear installations undergoing decommissioning (Chinon A1, A2 and A3) is satisfactory. The inspections conducted in 2020 have more specif ically revealed prof iciency in on-site waste 54 ASN Report on the state of nuclear safety and radiation protection in France in 2020 REGIONAL OVERVIEWOF NUCLEAR SAFETY AND RADIATION PROTECTION