The environmental group has already taken heat for stunts at other nuclear plants. According to plant operator EDF two drones were used in the activists' latest antic.
Greenpeace France said Tuesday it had flown the drone – piloted by one of its activists – over Bugey nuclear plant (pictured above), near Lyon. The pilot then crashed the Superman-shaped unmanned aircraft against the wall of the facility's spent-fuel pool building.
"The action again highlights the extreme vulnerability of this type of buildings, which contain the highest amount of radioactivity in nuclear plants," Greenpeace said.
State-controlled EDF, which manages the plant, said that two drones had flown over the facility. French police intercepted one of them, it added.
"The presence of these drones had no impact on the security of the installations," EDF said in a statement, adding that it planned to file a police complaint against Greenpeace.
The latest drone "attack" follows a series of Greenpeace stunts, which the environmental group claims have been staged to expose the weakness of French nuclear plants.
In October last year, Greenpeace activists breached security and launched fireworks over EDF's Cattenom nuclear plant.
"Spent-fuel pools must be turned into bunkers in order to make nuclear plants safer," said Yannick Rousselet, Greenpeace France's chief nuclear campaigner.
EDF insists the spent-fuel pool buildings can withstand natural disasters and accidents.
The French parliament ordered an investigation into nuclear security. A parliamentary committee is due to present its report on Thursday.
In February, a French court handed suspended jail sentences – along with fines to several Greenpeace activists.