France’s energy Achilles’ heel: How jellyfish and heatwaves slow nuclear reactors

France’s nuclear power system has encountered an unlikely obstacle: jellyfish. Last summer, four reactors at the Gravelines plant in northern France were shut down after jellyfish entered the area where the facility draws seawater.

The episode, encouraged by climate change and Europe’s rising temperatures, disrupted the plant’s operations. EDF has installed surveillance cameras and prepared fishing boats to intervene if the problem returns this summer.

Heat itself is creating a broader challenge. French nuclear reactors use river and ocean water to keep their temperatures within operating limits. During heatwaves, that water becomes too warm for the cooling systems, forcing plants to limit electricity production.

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Our citizens must have full confidence in our ability to produce energy even under such conditions.

In July, high temperatures prompted EDF to shut three of France’s 57 reactors and reduce production at seven others, according to a company statement. A similar situation occurred the previous month, when record temperatures led to three reactor shutdowns and reduced output at five more. Total electricity production fell by 8.7% as demand rose because people used air conditioners.

None of the shutdowns caused power cuts. Still, Europe’s accelerating warming has become a serious issue for France’s energy strategy. The country relies on nuclear power for roughly 60% of its electricity and is also trying to use that source to attract investment from energy-intensive industries, including artificial intelligence and cloud computing.

EDF chief executive Bernard Fontana said, “Our citizens must have full confidence in our ability to produce energy even under such conditions.” Energy Minister Maud Bregeon told RTL, “What we are experiencing is something ordinary. Every year, nuclear power plants reduce their production when the temperature exceeds a certain threshold.” Opponents of nuclear power, however, see the episodes as evidence of the system’s vulnerability. The left-wing France Unbowed party has questioned whether France can continue to rely on the technology.

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What we are experiencing is something ordinary. Every year, nuclear power plants reduce their production when the temperature exceeds a certain threshold.