"At no time was the situation threatening," the French Nuclear Safety Authority said in a statement.
Late on Dec. 27, after severe storms had pounded southern France, circuits and pumps on two nuclear reactors near Bordeaux were inundated by flood waters, damaging "important equipment," the statement said.
The reactors were shut down and remain out of operation.
The accident was rated a Level 2 on an international scale ranging from 1 to 7. The highest classification, Level 7, corresponds to an accident on the scale of Chernobyl.
The situation is now stable and new measures are being put into place to prevent a reoccurrence, the Nuclear Safety Authority said.
It added, however, that the reactors would not be restarted until measures are taken to protect them from exceptional weather conditions. That will keep them out of operation for at least several weeks, officials said.
"We had a serious nuclear incident," Jean-Louis Charriere, director of the Blayais plant, told French radio. He said that "several meters" of water flooded the two reactors.
France is one of the world's most nuclear-dependant countries, getting 77-percent of its power from nuclear energy.
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