"A Greenpeace drone placed a distress smoke signal on the roof of the [spent fuel] pool of Orano nuclear facility in [the city of] La Hague (France) to highlight the vulnerability & saturation of this building. It contains the equivalent of 100 irradiated nuclear cores," Greenpeace said via its official Twitter feed.
The environmental activists also posted photos and drone footage demonstrating bright red smoke spreading from an object placed on the roof of the building, which stores the largest amount of radioactive materials in the world, according to Greenpeace.
"What is more shocking is that this roof, made of simple sheet metal, is far too fragile to prevent a malicious act coming from the air," Greenpeace said in a separate statement, published on its official website.
The group has repeatedly raised the alarm about the decrepit condition of other French nuclear facilities, notably, the Bugey, Cattenom and Cruas nuclear power plants, built between the 1960-80s, and their vulnerability to modern-day threats.