Jellyfish swarm shuts down Gravelines nuclear plant on same date for second year running

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Aug. 11 is quickly becoming jellyfish invasion day at the Gravelines nuclear power plant in northern France.

Despite spending hundreds of thousands of euros to protect the plant from a jellyfish swarm like the one that saw reactors shuttered on Aug. 11, 2025 , French utility provider EDF on Tuesday was again forced to bring the parts of the facility offline due to the presence of “several dozen tons” of jellyfish blocking pumping systems.

“On-site teams are fully mobilized to ensure the safety of the facilities and to reconnect the reactors to the national power grid,” EDF said in a statement.

Three fishing vessels are now “constantly patrolling off the coast of the plant” to conduct “preventive fishing operations […] 24/7,” the company added.

Tuesday’s jellyfish invasion comes a the latest in a series of climate change-driven incidents that have affected French nuclear energy during a particularly infernal summer .

Nuclear power plants are typically built by rivers or on coastlines so they can use nearby water sources to cool their reactors. But a record number in France this summer have been forced to temporarily shut down due to heatwaves and droughts affecting their water supply.

Rising sea temperatures have made jellyfish swarms more common along the French coast in recent years, and those swarms can affect a plant’s ability to bring in seawater — which is what happened at Gravelines. Following last year’s incident at the plant along the North Sea, EDF installed cameras and deployed fishing boats to monitor the situation.

While the vessels “prevented a massive influx of jellyfish” on Saturday and Sunday, they were eventually overwhelmed as the swarm grew from “about 100 kilograms” to “several dozen tons,” the French state-owned utility giant said.

Opponents of nuclear energy were quick to jump on the incident.

“This only highlights that nuclear power plants are ill-equipped to deal with the consequences of climate change,” the French branch of Greenpeace said in statement.