Strikes by workers reduced output from French nuclear and hydropower stations on Thursday morning, data from power group EDF showed.
The 24-hour strike by French electricity union FNME over wage demands, pensions and purchasing power as inflation spirals across Europe reduced nuclear power generation by 3.3 gigawatts (GW) by 0720 GMT and by 610 megawatts (MW) at hydropower stations.
Five reactors were affected by the strike, with the disruption representing about 8.5% of total production on Thursday morning, the data showed.
French nuclear power output is at a 30-year low around 26.5 GW owing to an unprecedented number of outages at EDF's fleet of 56 reactors, with more than half of offline because of corrosion issues and scheduled maintenance.
The country is currently a net importer of 7.5 GW of power from Spain, Britain, Germany, Belgium and Switzerland, data from grid operator RTE shows, having become a net importer this year for the first time since records began in 2012.
The 1.3 GW Nogent 1 reactor is shown as offline because of the strike. The reactor also went offline on Wednesday with an unplanned outage after a water supply regulation failure in a cooling circuit in the non-nuclear part of the facility. (Reporting by Forrest Crellin Editing by Alison Williams and David Goodman