France's state-owned energy group EDF temporarily shut down three nuclear reactors on Sunday and warned that seven others may need to adjust their output as the country's third heatwave since May continues to push river temperatures higher. The move, required by environmental regulations, aims to prevent the release of excessively hot water into rivers already warmed by the extreme weather.
Nuclear power plants rely on river water for cooling, then discharge the heated water back into the waterway. Under French law, the temperature of that discharge must stay within limits designed to protect aquatic ecosystems. With the current heatwave pushing ambient river temperatures up, EDF said it had no choice but to comply.
“There is no nuclear safety risk. Reactors are capable of operating under high-temperature conditions. These limits are intended to protect aquatic flora and fauna,” an EDF spokesperson told Euronews.
The three reactors currently offline are Unit 2 at Golfech (1,300 MW), Unit 3 at Bugey (900 MW), and Unit 2 at Chooz (1,450 MW). Together, they represent about 3.65 GW of capacity, roughly 6 percent of France's total installed nuclear fleet of around 61 GW. According to EDF, Bugey Unit 3 is scheduled to remain offline until 19 July, Golfech Unit 2 until 22 July, and Chooz Unit 2 until 25 July, though these dates may change depending on weather forecasts.
Seven additional reactors may be required to reduce their power output during the hottest parts of the day, the company said. The scheduling and duration of these environmentally driven outages will be adjusted as forecasts evolve.
Economic and Grid Implications
The shutdowns come at a time when France's electricity grid is already under strain from high demand for air conditioning and refrigeration. On Saturday, the French economy ministry issued an exemption to the temperature limits for the Rhône around the Bugey plant, valid until 20 July, “to ensure the security of the power grid.” The exemption allows EDF to continue operating the reactor at reduced power even if discharge temperatures exceed normal limits.
This is the second time in recent weeks that EDF has had to halt reactors due to extreme heat. A record-breaking heatwave in June also forced temporary shutdowns. Despite these disruptions, EDF insists the impact on annual generation is minimal. “Since 2000, production losses resulting from high river water temperatures and low river flows have represented, on average, 0.3% of the French nuclear fleet’s annual electricity generation,” the spokesperson said.
Nevertheless, the repeated heat-related outages highlight a growing vulnerability for France's nuclear-heavy energy system as climate change intensifies. The country relies on nuclear power for about 70 percent of its electricity, making it particularly exposed to heatwaves that reduce cooling efficiency and force regulatory curtailments.
EDF has an adaptation plan to address these risks, covering its nuclear, hydropower, and island energy operations in France. The company disclosed in early 2026 that the estimated cost of the plan is €8.7 billion over the next 15 years. Among the measures under consideration is a system to cool water discharged from cooling towers before it is released into the environment, a technology already in use at the Civaux Nuclear Power Plant.
For its hydropower business, EDF is focusing on improving flood management, maintaining generation during low-flow periods, and supporting multiple uses of water resources.
The heatwave has also affected other sectors. Paris landmarks close early as third heatwave hits France, and a major wildfire rages in Fontainebleau forest south of Paris. Across Europe, June heatwaves linked to over 10,000 excess deaths across Europe, underscoring the broader human and economic toll of extreme heat.
As France and the rest of Europe grapple with more frequent and intense heatwaves, the tension between energy security and environmental protection is likely to become a recurring challenge for policymakers and grid operators alike.
