Chooz nuclear plant restarts after a 3-month drought shutdown

On July 11, 2026, EDF, France's main electricity producer, shut down one of the two reactors at the Chooz nuclear plant, in France's Ardennes region, because the Meuse river was too low. The second one stopped on August 1, and the first one only restarted on October 26, according to Révolution Énergétique, a French energy news site.

Key takeaways

• Chooz was offline for about three months: reactor 2 shut down on July 11, reactor 1 on August 1.
• Reactor 1 (1,450 MW) restarted on October 26, after Storm Austen raised the level of the Meuse.
• Reactor 2 was expected to restart in the following days, with no confirmation in the article we read.
• According to RTE, France's grid operator, heat and drought cost the French nuclear fleet up to 10 TWh this summer, including nearly 4 TWh at Chooz.

July 11: the Meuse drops to 21.3 m³/s

Reactor 2 was shut down as a precaution when the flow of the Meuse fell to 21.3 cubic meters per second, according to EDF information reported in the press. At that point, EDF gave no restart date: everything depended on how much rain would fall. On August 1, at 23:05, reactor 1 followed, taking the whole plant offline.

Why does a drought shut down a nuclear plant?

Because a plant draws water from a river to cool itself, and that water has to stay plentiful enough. At Chooz, the limit also comes from a legal text: the French-Belgian agreement of September 8, 1998 on managing the waters of the Meuse sets thresholds, and EDF shuts down the reactors to respect them when the flow drops.

Data centers raise the same kind of question: they also depend on water for cooling, as we explained in the article on how much water data centers drink.

Chooz wasn't the only one to suffer. According to Révolution Énergétique, drought and heat cut the output of several reactors in the fleet, and the Civaux and Bugey plants got exemptions to exceed the temperature limits on the water they release.

October 26: Storm Austen refills the Meuse

In the end, water fixed the problem. Storm Austen, which cut power to nearly 300,000 homes, raised the level of the Meuse, allowing EDF to restart reactor 1, rated at 1,450 MW, on October 26. The same event both battered the grid and got the plant running again.

4 TWh lost at Chooz out of 10 for the whole fleet

An estimate by RTE published on September 21, 2026 puts nuclear output lost this summer to heat and drought at up to 10 TWh. Chooz reportedly accounts for nearly 4 TWh of that, or 4 billion kilowatt-hours. Révolution Énergétique doesn't give a loss figure for the plant.

€9 billion for the next drought

EDF has launched a €9 billion program over 15 years to manage water better: use less of it in its plants and release cooler water into rivers. An earlier program, "Grands Chauds" ("Big Heat"), dates back to 2008. The outlet expects summers like 2026 to become more frequent with climate change.