Grand Est Chooz nuclear power plant The Chooz NPP operated by EDF is situated in the municipality of Chooz, 60 km north of Charleville‑Mézières, in the Ardennes département. The site accommodates the Ardennes NPP, called Chooz A, comprising reactor A (BNI 163), operated from 1967 to 1991, for which the final shutdown and decommissioning operations were authorised by Decree 2007-1395 of 27 September 2007, and the Chooz B NPP, comprising two 1,450 MWe reactors (BNIs 139 and 144), commissioned in 2001. Reactors B1 and B2 in operation ASNR considers that the performance of the Chooz B NPP in terms of nuclear safety and environmental protection is consistent with ASNR’s general assessment of EDF’s NPPs. It stands out favourably in terms of worker radiation protection. In terms of facility operation, ASNR notes a trend towards improvement, particularly in terms of compliance with requirements for facility supervision, alarm management and documentation management, which should be confirmed in 2026. However, better coordination between the professions handling reactor operation and those handling maintenance, as well as stricter compliance with procedures, are expected, as these two areas have been implicated in several significant events. In terms of maintenance, the year was marked by an outage for maintenance and refuelling of Reactor 1, which involved a high volume of activities. This was generally under control, despite some malfunctions encountered during restart operations. However, a number of shortcomings in the performance of maintenance activities were noted, some of which led to significant safety events. In terms of radiation protection, ASNR considers that the progress noted in 2024, particularly on issues relating to the radiological cleanliness of facilities, has been confirmed in 2025. However, occasional shortcomings in the radiation protection culture and in controlling the risk of contamination spreading to worksites were noted in 2025. The licensee is expected to make a special effort in these two areas in 2026. Regarding environmental protection, ASNR considers that the organisation of the site remains satisfactory. A number of areas for improvement have been identified, relating to the liquid containment of effluents and the performance of water sampling and liquid effluent discharge equipment. Finally, in terms of occupational health and safety, the maintenance outage of reactor 1 was marked by several accidents or “near misses” linked to the risk of falling loads. They highlight the need for better risk analysis upstream of operations and better coordination between the licensee and its outside contractors. Reactor A undergoing decommissioning In 2025, operations linked to the extraction of the reactor vessel were the main activities carried out in the reactor cavern (HR). Once the vessel had been lifted and placed on a transit stand, the insulation covering its lower section could be removed and cut away. The reactor pit has been sealed off with a device that restores the watertightness of the pool floor and also serves to support the reactor for the next stages of cutting, scheduled for 2026. In the auxiliary cavern (HK), operations to decommission the remaining equipment continued. With regard to nuclear safety and worker radiation protection, 2025 saw an increase in the number of significant events and internal contamination, despite the action taken by the licensee in this area over several years. Analysis of these different situations, as well as inspections carried out throughout the year, including reactive inspections following events, led ASNR to ask that preventive measures be strengthened, particularly with regard to worker radiation protection. On 26 December 2025, it also decided to place the site under tightened surveillance for all decommissioning activities until the results once again meet expectations in terms of nuclear safety and worker radiation protection. In terms of the environment, ASNR’s the performance considered generally satisfactory by ANSR in recent years has been maintained in 2025. THE INSTALLATIONS AND ACTIVITIES TO REGULATE COMPRISE: ▸ basic nuclear installations: • the Cattenom NPP (4 reactors of 1,300 MWe), • the Chooz A NPP (1 reactor of 305 MWe undergoing decommissioning), • the Chooz B NPP (2 reactors of 1,450 MWe), • the Fessenheim NPP (2 reactors of 900 MWe in final shutdown status, decommissioning scheduled to begin in 2026), • the Nogent-sur-Seine NPP (2 reactors of 1,300 MWe), • the CSA storage centre for short-lived low- and intermediate-level radioactive waste (LL/ILW-SL) located in Soulaines‑Dhuys in the Aube département; ▸ the Cigéo geological disposal project for long-lived high- and intermediate-level radioactive waste; ▸ small-scale nuclear activities in the medical sector: • 14 external beam radiotherapy departments, • 5 brachytherapy departments, • 19 nuclear medicine departments, • about 100 computed tomography departments, • 70 centres performing fluoroscopy-guided interventional procedures, • some 2,300 medical and dental radiology centres; ▸ small-scale nuclear activities in the industrial, veterinary and research sectors: • about 200 industrial and veterinary activities subject to licensing and registration systems, • 34 companies exercising an industrial radiography activity, • about 37 public or private research units; ▸ activities associated with the transport of radioactive substances; ▸ ASNR-approved laboratories and organisations: • 6 laboratories approved for taking environmental radioactivity measurements, • 2 organisations approved for measuring radon. Chap.7 Chap 6 Chap.5 ABSTRACTS – ASNR Report on the state of nuclear safety and radiation protection in France in 2025 59
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