Punishing heatwave exposes cracks in France's nuclear power fleet
EDF, France's electricity operator, shut down one reactor at its Golfech nuclear plant on the Garonne on Monday after river temperatures approached the site's operating limit of 28C. Output has also been reduced at reactors in Bugey on the Rhône and Nogent-sur-Seine.
The disruption remains limited. France's grid operator RTE said electricity supplies remain secure. EDF said the loss of 2.2 gigawatts – about 3.5 percent of the country's nuclear capacity – does not threaten the balance between supply and demand.
But ecologists and some energy experts say the shutdowns are part of a growing pattern that raises questions about how a nuclear fleet largely designed in the 1970s will cope with a warming planet.
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Water shortages
"Nuclear power is clearly a 20th-century technology that is ill-suited to the 21st," said Yves Marignac, an independent nuclear expert and spokesperson for the think tank négaWatt.
"The warning signs are becoming stronger every year."
France generates around 70 percent of its electricity from nuclear power – more than any other country in the world. Most of its 56 reactors are built beside rivers or the coast because they require vast quantities of water for cooling.
"We're talking several cubic metres per second, sometimes more," Marignac said.
EDF figures reported by French daily Le Monde show about 15.3 billion cubic metres of water are withdrawn from rivers each year to cool France's nuclear plants, making the sector the country's second-largest user of water with 31 percent, behind agriculture on 45 percent and ahead of drinking water on 21 percent.
"Given projections of a drop of up to 40 percent in available freshwater in France by 2050, maintaining both agriculture and the nuclear fleet in their current form becomes extremely difficult," Marignac said.
Most of France's 18 nuclear plants are inland. As rivers shrink during dry periods there is less water available for cooling. Warmer rivers also cannot absorb as much heated cooling water without harming fish and other wildlife.
"We now see these limitations every summer," Marignac said. "It's never the whole fleet and usually only for relatively short periods. But each year the alert becomes a little stronger."
French environmental regulations require EDF to reduce output when river temperatures reach certain thresholds, around 28C, to protect local ecosystems.
"The choice becomes one between producing electricity and preserving ecosystems," Marignac said.
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Growing pressure
The reactors most exposed are those on the Rhône and Garonne, including Bugey, Saint-Alban, Cruas, Tricastin and Golfech, where operators depend on enough cool water to remain within environmental limits.
EDF said climate-related restrictions currently reduce annual nuclear production by around 0.3 percent. Without adaptation, the company estimates that figure could rise to around 1.5 percent by 2050.
The state-owned utility plans to invest 8.7 billion euros by 2040 to adapt its nuclear and hydroelectric power stations to a warmer climate.
Marignac said some of the risks are also becoming harder to predict.
Last August EDF temporarily shut down the Gravelines nuclear plant on the North Sea coast after a "massive and unpredictable presence of jellyfish" clogged its filter system. Algae blooms, which are also increasing because of warmer temperatures and greater use of nitrate-based fertilisers, have also disrupted water intake systems.
"We're entering a period where climate change and biodiversity loss are producing changes that are no longer linear," Marignac said. "That makes them much harder to anticipate."
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Future designs
France's planned EPR2 reactors are expected to rely on the same basic cooling system as existing plants.
"The cooling principle doesn't change at all," Marignac said. "Each reactor is actually more powerful, so the cooling requirements are even greater."
Cooling towers can reduce the amount of heated water released into rivers but cannot remove the need for large volumes of water in the first place, Marignac said. Retrofitting them to older plants, while possible, is technically difficult and expensive.
EDF is studying other options, including cooling water before returning it to rivers, but Marignac said these are not long-term solutions.
Does France's emphasis on nuclear power guarantee its energy independence?
"The technology is fundamentally rigid. When you want to adapt it, you're forced into technical workarounds – bolting a second cooling loop onto the first, and so on.
"You draw water to cool the reactor, that heats the water, then you use the reactor's own electricity to cool it again before discharge. It's a sticking plaster on a design that's no longer fit for purpose."
Supporters of nuclear power have long argued it helps ensure France's energy sovereignty in an increasingly unstable world. Marignac argued renewable energy offers a more sovereign path in the long term.