Image Courtesy: AFP

France has temporarily shut down several nuclear reactors after an intense heatwave pushed river temperatures beyond environmental limits, forcing the country’s largest electricity producer to reduce output to protect freshwater ecosystems.

State-owned utility EDF took two reactors offline at the Nogent-sur-Seine and Bugey nuclear power plants after the Seine and Rhône rivers became too warm to safely absorb additional cooling water. Another reactor at the Golfech plant had already been shut down earlier in the week, while power output at several other facilities was reduced. The measures were taken to protect aquatic life rather than address any safety concerns at the reactors themselves, according to Le Monde.

Most French nuclear plants use river water to cool their reactors before returning it to the environment. During prolonged heatwaves, river temperatures rise significantly, and releasing warmer water back into already-heated rivers can threaten fish, plants, and other wildlife. Environmental regulations therefore require operators to reduce generation or temporarily halt reactors when temperature thresholds are exceeded.

France relies on nuclear power for roughly two-thirds of its electricity, making it one of the world’s most nuclear-dependent nations. Despite the temporary reactor shutdowns, grid operator RTE said the country’s electricity supply remains secure and that sufficient generating capacity is available to meet demand.

The reduced output has still affected energy markets. Reports indicate that the heatwave cut French nuclear generation by about 4 gigawatts, roughly 7 percent of national electricity demand at one stage. Combined with higher electricity consumption for cooling and weaker wind generation, the reduced supply pushed wholesale electricity prices in both France and Germany to their highest levels since early 2025.

The latest shutdowns highlight a growing challenge for the nuclear industry as climate change increases the frequency and intensity of extreme heat events. While nuclear power remains a key source of low-carbon electricity, many existing plants were designed around historical river temperatures that are becoming less predictable.

With much of Western Europe experiencing record-breaking temperatures, energy experts expect utilities to increasingly explore upgraded cooling systems and other adaptation measures to maintain reliable electricity generation while protecting surrounding ecosystems.