How much nuclear power capacity was taken offline due to jellyfish swarms at France's Gravelines plant?

A massive influx of jellyfish forced Electricite de France SA to shut down three units and reduce output at a fourth unit at its Gravelines nuclear power plant, taking approximately 3.2 gigawatts of capacity offline.

Why are jellyfish swarms affecting nuclear power generation at Gravelines, and what environmental conditions contributed to this event?

Gravelines, located on France’s northern coast, draws seawater for reactor cooling through intake systems that can become clogged by jellyfish; unusually high coastal water temperatures — linked to a series of summer heat waves across Europe — triggered a jellyfish bloom, leading to the clogging of filter drums, as occurred similarly at the same site last year.

Jellyfish Swarms Knock Out 3.2 Gigawatts of French Nuclear Power

Aug 11, 2026

EDF shut three nuclear units at Gravelines due to jellyfish clogging cooling systems, removing 3.2 gigawatts of capacity during extreme heat waves that strain European power grids.

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