France Cuts Nuclear Output by Record 6.3 Gigawatts as Rivers Hit Cooling Limits

France reduced nuclear output across eight reactors by 6.3 gigawatts on July 13—the largest single-day cut this summer—as river temperatures approached regulatory discharge caps. Environmental rules limit heated water returned to rivers; warm, low water compounds the constraint. This marks the third significant curtailment since June's record heat, driven by record Atlantic sea surface temperatures sustaining drought conditions. For a nation deriving two-thirds of electricity from nuclear, thermal constraints are shifting from anomaly to structural summer risk.