RTE data showed that output at St. Alban 1 was at 260 MW by 2200 GMT.
The power systems operator said on Sunday that EDF had been warned of a 24-hour strike at its power generation units in France starting Monday Jan. 21 at 2000 GMT.
RTE said the strike had also impacted electricity output at EDF's 1,200 MW Cordemais 4 and 5 coal-fired power generators. Output at Cordemais 4 was down over 32 percent at 392 MW, while the similar capacity Cordemais 5 was offline.