French nuclear authorities are reviewing a reported safety violation at the Cattenom power plant where technicians kept operating for six hours after identifying a blocked valve in emergency ventilation equipment.

A blocked valve in the Cattenom nuclear power plant's fuel building ventilation system was discovered on 3 June, potentially compromising emergency safety systems.

Plant operators continued work for nearly six hours across two sessions despite regulations requiring shutdown within one hour of ventilation failure.

While operator Électricité de France (EDF) maintains there was no immediate danger, the breach prompted an official Level 1 safety incident report to nuclear authorities on 10 June.