France's oldest nuclear power plant, Fessenheim, was shut down on Saturday following an incident at the facility away from the reactor which did not pose any danger, operator EDF said.
The accidental closing of a valve controlling the steam supply to the turbine generator automatically shut down Fessenheim's reactor 2. Technicians were working on the issue and a restart date had yet to be determined, an EDF spokeswoman told Reuters.
Fessenheim's reactor 1, the oldest in France, has been inactive since April 9 when a leak was detected in a water supply pipe.
"These are two incidents that have no bearing on the security of the plants nor for the environment," the spokeswoman said.
The 1,800-megawatt plant is unpopular due to its age and location in an earthquake-prone zone of eastern France and has attracted media attention since President Francois Hollande said in his electoral pledge he planned to shut it down by 2016.
Fessenheim's two 900-megawatt reactors have been in operation since 1977.
In a statement, France's Greens party reiterated its opposition to the aging plant, saying: "Our oldest nuclear reactors are fragile and must be closed."
(Reporting By Jean-Baptise Vey, Writing by Alexandria Sage, editing by Rosalind Russell)