French authorities say half of nuclear power plants are now offline for maintenance or defects, at a time of soaring demand for electricity amid the energy crisis in Europe.
Energy supplier Electricité de France (EDF) said some 28 of the country's 56 reactors were shut down due to routine maintenance or defects on Friday.
The latest shutdown forced EDF to buy electricity from the European grid "to compensate the lack of production of our nuclear plants."
The power firm which supplies all of France's atomic energy, said it was "impossible to qualify the source of energy production."
A quarter of all electricity in the EU comes from nuclear power produced in a dozen countries from an aging fleet that was mostly built in the 1980s. France, with 56 reactors, produces more than half the total.
The nuclear plant shutdown came at a time that the European continent struggles with high prices and market uncertainty amid the war in Ukraine.
The European Union (EU) is struggling to reduce its dependence on Russian oil and gas to zero by the end of 2027.
The member states are now divided over how aggressively to move against Russian energy, in response to the military campaign in Ukraine.
Russia provides more than a quarter of EU crude oil imports.
Talks to find ready alternatives to Russian fuel have also sparked a political divide in Europe over nuclear power.
Nuclear energy could help solve Europe’s dependence on Russia, but according to experts, it is not going to happen overnight.