Jellyfish swarm shutters another French nuclear reactor

A jellyfish swarm reduced output by 2.4 gigawatts at French utility EDF’s Paluel nuclear plant after entering the filters of the pumping station, EDF said on Thursday (September 4, 2025), the second time jellyfish have impacted production in a month.

Electricity production at the 5.2 GW Paluel nuclear plant in northern France was nearly cut in half late on Wednesday (September 3, 2025) as the number 4 reactor was shut down and power at the number 3 reactor was reduced in a preventative manner, EDF said.

The Paluel plant is connected to and cooled by waters from the English Channel, where both native and invasive jellyfish have experienced wider breeding windows due to warmer temperatures, increasing the size of swarms.

Reactor number 1 is operating at full capacity and number 2 is currently shut down for maintenance.

The Gravelines nuclear plant was shuttered in mid-August after a separate “massive and unpredictable” swarm of jellyfish entered its cooling systems.

This is not the first time that jellyfish have disrupted nuclear plants in general. Scotland’s Torness faced similar problems in 2011, while Gravelines itself was disrupted in 1993.

Scientists warn that such events could become more common due to factors including global warming, the arrival of invasive marine species, habitat loss of predators, and over-fishing.