Thousands of demonstrators have formed a human chain outside France's oldest nuclear power plant to demand the site be closed as the government considers whether to extend its life by a decade.
The plant at Fessenheim, in Alsace, has become a flashpoint in the renewed debate over nuclear safety in France following the Fukushima disaster in Japan.
The demonstrators fear the site is vulnerable to earthquakes and flooding.
Some 5,000 mostly German demonstrators stretched out over about 4km outside the plant on Sunday in a protest organised by French, Swiss and German associations, supported by France's socialist and green parties.
The plant's location near the German border has also made Fessenheim a point of tension between France, which is heavily reliant on its 58 nuclear reactors and has defended their safety, and Germany, which has decided to abandon nuclear power.
France's Ecology Minister says there will be no decision until a report from the nuclear safety watchdog early next month and the results are in from safety tests set up in the wake of Fukushima.
The No. 1 reactor at Fessenheim has been in service since 1977 and is is operated by French power group EDF.