Jellyfish Swarms Force French Nuclear Plant to Shut Down Four Reactors

The Gravelines nuclear power plant, located on the English Channel coast in northern France, has shut down four of its six operational reactors after jellyfish swarms clogged the seawater intake and filtration systems critical for cooling the plant's reactors.

Gravelines is the largest nuclear power plant in Western Europe by installed capacity. The simultaneous loss of four of six units represents a significant reduction in output, with implications for France's electricity grid, which relies heavily on nuclear power for around 70% of its electricity generation.

Jellyfish blooms blocking cooling water intakes are a known phenomenon at coastal power plants worldwide, but the scale of the disruption at Gravelines is considered exceptional. Marine biologists have linked increasingly frequent and large jellyfish blooms to rising sea temperatures, overfishing of predatory species, and nutrient runoff from agriculture.

Operators EDF said the affected reactors will remain offline until the jellyfish concentrations in the coastal waters dissipate sufficiently to allow normal filtration operations to resume. No radiation hazard was reported, as the plant's safety systems functioned as designed.

France's grid operator issued a call for electricity conservation measures while the reactors remain offline, warning of potential supply tightness during peak demand hours.