From his humble Starting as a glacier in the Swiss Alps, the Rhône River is rapidly turning into one of the world’s most industrialized waterways. As it winds its way through southern France towards the Mediterranean, its cool water is drawn into boilers, sucked through pipes as coolant, diverted to agriculture. Among its largest customers is a battalion of nuclear reactors. Since the 1970s, the river and its tributaries have helped generate about a quarter of France’s nuclear energy.
But in recent weeks this has not been the case. Amid a slow-burning heat wave that has killed hundreds and triggered intense forest fires across Western Europe, and combined with already low water levels due to drought, Rhône’s water has become too hot for the job. It is no longer possible to cool reactors without expelling water downstream that is so hot that it extinguishes life in water. So a few weeks ago, the Électricité de France (EDF) started shutting down some reactors along the Rhône and another major river in the south, the Garonne. It is now a well-known story: Similar shutdowns due to drought and heat took place in 2018 and 2019. This summer’s cuts, combined with malfunctions and maintenance on other reactors, have helped reduce France’s nuclear power production by almost 50 percent.
Of all the low-carbon energy sources that are likely to be needed to combat climate change, nuclear power is usually considered to be the least disruptive. It is the reinforcement that is called in when the weather does not cooperate for other carbon-free energy sources, such as wind and solar. But the nuclear industry faces its own climate risks.
Water problems – too much or too little – are more commonly associated with hydropower dams, which have struggled to maintain production in arid places such as the American West. But as the Swedish historian Per Högselius puts it, much of today’s nuclear technology is not about splitting atoms, but about dealing with major aquatic concerns. Nuclear technicians are known for referring to their craft as a very complicated way of boiling water and producing steam that rotates turbines. But it usually takes a lot more to keep the reactor cool. That is why there are so many facilities by the sea and along large rivers like the Rhône.
Lots of other industries are affected by warmer rivers, including large factories and power plants running on coal and gas. But nuclear power plants are unique because of their enormous size and the key role they play in keeping energy networks online in places like France. And warming and dwindling rivers are not the only climate challenges they face. On the coasts, a combination of sea level rise and more frequent and intense storms means increased risk of flooding. Researchers have also pointed to other, more unusual challenges, such as more frequent algae blooms and exploding jellyfish populations, which can clog water pipes.
Nuclear power plants are also built to last well into the future, with lifetimes extending half a century or more. Many were built in the 1970s and 80s – long before regulators thought to address climate-related threats they would eventually encounter, explains Natalie Kopytko, a researcher at the University of Leeds who has dug into nuclear regulatory frameworks to look for climate considerations. “I saw absolutely nothing about climate change, which was pretty scary,” she says. Where Kopytko saw the climate relied on, the plans assumed that current weather patterns would hold up well into the future.