A massive swarm of jellyfish has forced the shutdown of three reactors at France's Gravelines nuclear power plant. The incident occurred in early August 2026, marking the second consecutive year that a jellyfish invasion disrupted operations at the facility on nearly the exact same date.

 

Swarming jellyfish overrun French nuclear plant on same date two years in a row

A massive swarm of jellyfish has forced the shutdown of three reactors at France's Gravelines nuclear power plant. The incident occurred in early August 2026, marking the second consecutive year that a jellyfish invasion disrupted operations at the facility on nearly the exact same date.

 

Impact on the Power Supply

• Reactors Affected: Three 900-megawatt production units automatically shut down, and output was heavily reduced at a fourth.
• Capacity Lost: The disruption took approximately 3.2 gigawatts of capacity offline.
• Grid Strain: The shutdown coincided with a major heatwave driving up seasonal electricity demand.
• Safety Status: Plant operator Electricité de France (EDF) confirmed there is no impact on safety, personnel, or the environment.

The Cause of the Shutdown

The Gravelines nuclear power station, located near Dunkirk, relies on water drawn from a canal connected to the North Sea to cool its systems. Millions of jellyfish were sucked into the pumping stations, clogging the mechanical filter drums and triggering automatic system halts to prevent overheating.

Why This is Happening

Marine biologists and climate scientists note that these repeated occurrences are driven by a combination of environmental pressures:

• Warming Seas: Higher ocean temperatures expand the reproductive windows for jellyfish, accelerating their population growth.
• Overfishing: Commercial depletion of natural jellyfish predators and food competitors leaves vast resources for blooms to grow unchecked.
• Invasive Species: Ships carrying ballast water have introduced aggressive varieties like the Asian moon jellyfish into the North Sea ecosystem.

Immediate Response and Cleanup

To resolve the blockage, EDF teams mobilized with vacuum trucks to clear the jammed filters. The company has also deployed local fishing boats to conduct targeted trawling operations offshore to break up remaining jellyfish densities before they enter the intake canals