France recorded its hottest day since 1947 on June 23, with temperatures topping 44 degrees Celsius. The heat didn’t just break records – it started shutting down nuclear reactors.
Unit two at the Golfech nuclear plant in southern France went offline on June 22 when the Garonne River, which cools the reactor, got too warm. French regulations limit how hot the return water can be, and the river was approaching 28 degrees Celsius. The operator, EDF, had no choice but to shut it down.
Unit one was already offline for planned maintenance and refueling. So both reactors at Golfech went dark at the worst possible time.
EDF is also limiting output at other reactors across France. One unit at Nogent-sur-Seine was ramped down as of Tuesday, with more expected to follow. During a July 2025 heat wave, at least seven gigawatts of nuclear capacity went offline across the country – more than the entire grid of Ireland.
This time, France’s grid operator RTE says outages shouldn’t be drastic enough to affect the ability to meet demand. But the pattern is clear: as heat waves become more frequent and more severe, nuclear plants that depend on river water for cooling will face more constraints.
It’s a problem that’s only going to get worse. European grid operators historically planned maintenance around winter peaks. Now summer is becoming the stress season, and the infrastructure isn’t fully adapted yet.
