Heatwave: EDF shuts down three nuclear reactors to protect rivers

In response to the heatwave gripping France, EDF shut down three nuclear reactors on Sunday, representing 3,65 GW of capacity, to avoid releasing excessively hot water into already swollen rivers. Seven other units could see their output reduced in the coming days.

The reactors affected are Unit 2 at the Golfech nuclear power plant (1,300 MW), Unit 3 at Bugey (900 MW), and Unit 2 at Chooz (1,450 MW). Together, they represent approximately 6% of the 61 GW of France's nuclear fleet. According to current weather forecasts, Bugey 3 is expected to remain offline until July 19, Golfech 2 until July 22, and Chooz 2 until July 25, though these dates are subject to change depending on the weather.

The mechanism involved is well known: nuclear power plants draw water from rivers and streams to cool their reactors, then return it heated to the environment. When river temperatures rise due to heat waves, regulatory limits for thermal discharge can be exceeded. "There is no risk to nuclear safety. The reactors are capable of operating in high-temperature conditions. These limits are designed to protect aquatic flora and fauna," stated an EDF spokesperson.

However, on Saturday the Ministry of Economy granted a temporary exemption to the temperature thresholds applicable to the Rhône around the Bugey power plant, valid until July 20, "in order to guarantee the safety of the electrical network".

This is the third heatwave to hit France since May. On Sunday, more than a third of the country was under Météo-France's highest heatwave alert level. EDF had already had to shut down reactors during a record-breaking heatwave in June, making this Sunday shutdown the second of its kind in just a few weeks.

In the long term, the impact remains limited, according to the group: since 2000, production losses linked to high river temperatures and low flow rates have represented on average 0,3% of the annual production of the French nuclear fleet. EDF nevertheless asserts that it has a climate change adaptation plan, the cost of which has been estimated at €8,7 billion over fifteen years, to be announced in early 2026.

Among the options being considered is cooling the water from the cooling towers before it is released into the environment, a system already operational at the Civaux power plant. For hydroelectric power, EDF is working to improve flood management and maintain production during periods of low water. In island territories, the group is strengthening its electrical grids and its capacity to cope with extreme wind events.