Cattenom Nuclear Plant Reclassifies Safety Event as Level 1 Incident

On Thursday 5 November 2026, Luxembourg's Grand Ducal Fire and Rescue Corps (CGDIS) shared a communication from EDF, the operator of the Cattenom nuclear power plant across the border in France, concerning non-compliance with a permanent operating requirement on Production Unit 2.

According to EDF, the reactor containment building is a concrete structure housing the reactor vessel and other components of the primary circuit (nuclear zone). The containment consists of a double wall, with an inner wall made of prestressed concrete and an outer wall made of reinforced concrete, separated by an inter-containment space to ensure the leak-tightness of the reactor building.

To access the room located beneath the inter-containment space, personnel use an airlock consisting of two airtight doors, whose opening and closing are governed by the plant's operating rules.

On 9 May 2026, while Production Unit 2 was shut down for scheduled maintenance, a worker identified that the inner door of the airlock was partially open by a few centimetres. As soon as the deviation was detected, the door was closed and locked in accordance with the requirements.

Following investigations, the plant's teams concluded that the inner door had not been properly closed during the last access to the room on 26 November 2024. Nevertheless, since that date, the outer door of the airlock had remained closed and locked, meaning that the leak-tightness of the inter-containment space had been maintained throughout.

EDF stated that the anomaly had no consequences for the facilities, personnel or the environment. The event was initially reported to the French Nuclear Safety and Radiation Protection Authority (ASNR) on 13 May 2026 as a Level 0 significant safety event on the International Nuclear and Radiological Event Scale (INES).

Following an in-depth analysis of the applicable operating requirements, the plant's management reclassified the event as Level 1 due to non-compliance with a permanent operating requirement and notified the ASNR on Wednesday 4 November 2026.