Massive jellyfish swarm forces shutdown of 3 reactors at Gravelines nuclear plant in France

AKIPRESS.COM – Three of the six nuclear reactors at France’s largest nuclear power plant, Gravelines, have been shut down following a massive influx of jellyfish into its cooling systems, according to plant operator EDF.

The units were halted after filtering drums in the pumping stations became clogged by jellyfish drawn with North Sea water used for cooling. A fourth reactor’s output was reduced to 50% as a precautionary measure, while a fifth was already offline for scheduled maintenance. Only the sixth unit continues to operate at full capacity. Under normal conditions, the plant’s six reactors generate a combined capacity of 5,460 megawatts.

EDF emphasized that the incident poses no threat to safety, personnel, or the environment. The company noted that no new swarms have been observed, and system cleaning operations are nearing completion.

This is not the first occurrence at the plant; one year ago, Gravelines was forced to shut down entirely due to a similar jellyfish swarm. Following that incident, EDF introduced new monitoring and trapping protocols to mitigate future risks, including installing cameras in intake channels and filtering drums for early detection, as well as partnering with local fishing and sea rescue organizations to track and net jellyfish swarms before they reach the plant.

Experts attribute the surge in jellyfish populations to climate change and warming waters in the North Sea. The disruption comes as EDF already faces power generation constraints across France due to persistent heatwaves affecting Europe since May, with a fifth heatwave expected within the week that could further curtail French nuclear output.