Nuclear power plants are struggling to stay cool

From its humble start as a glacial trickle in the Swiss Alps, the Rhône River quickly transforms into one of the world's most industrialized waterways. As it winds through the south of France toward the Mediterranean Sea, its chilly water is drawn into boilers, sucked through pipes as coolant, deviated for agriculture. Among its biggest customers is a battalion of nuclear reactors. Since the 1970s, the river and its tributaries have helped generate about a quarter of France's atomic energy.

But in recent weeks that hasn't been the case. Amidst a slow-burning heat wave that has killed hundreds and sparked intense wildfires across Western Europe, and combined with already low water levels due to drought, the Rhône's water has gotten too hot for the job. It's no longer possible to cool reactors without expelling water downstream that's so hot as to extinguish aquatic life. So a few weeks ago, Électricité de France (EDF) began powering down some reactors along the Rhône and a second major river in the south, the Garonne. That's by now a familiar story: Similar shutdowns due to drought and heat occurred in 2018 and 2019. This summer's cuts, combined with malfunctions and maintenance on other reactors, have helped reduce France's nuclear power output by nearly 50 percent.