The board of state-run Electricite de France voted in January to approve the closure next year in principle. But the company says the board decided Thursday not to close the 40-year-old facility until a new-generation plant is online at Flamanville in western France.
Unions oppose shutting down the two reactors at the Fessenheim plant, near the German border. The company says it will lose too much money if it shuts down too soon.
The German government called last year for Fessenheim's closure. French President Francois Hollande pledged to shut the plant as part of his strategy to reduce France's exceptionally heavy dependence on nuclear power.