Jellyfish Swarms Force Shutdown of 3.2 GW at France's Gravelines Nuclear Plant Amid Heat Wave
Key Takeaways
- •A massive influx of jellyfish has forced EDF to shut down three reactor units at its Gravelines nuclear plant and reduce output at a fourth, removing approximately 3.2 gigawatts of capacity from the French grid.
- •The capacity loss represents roughly five percent of France's approximately 63 gigawatts of installed nuclear capacity, which typically supplies around two-thirds of the country's electricity.
- •Two of the affected reactors are scheduled to resume operations by Wednesday night, while the remaining two with a combined capacity of 1.8 gigawatts could stay offline until the end of the week.
- •EDF is simultaneously confronting output restrictions at inland nuclear sites along rivers where elevated water temperatures have compromised the ability to cool reactors without risking ecological harm.
- •The Gravelines facility experienced a comparable jellyfish-related shutdown last year, illustrating the increasing frequency of climate-driven disruptions to nuclear cooling systems across Europe.
A "massive influx" of jellyfish has forced Électricité de France SA (EDF) to shut down three reactor units at its Gravelines nuclear power plant and reduce output at a fourth, removing approximately 3.2 gigawatts of capacity from the grid at a time when soaring temperatures are driving up electricity demand across France. The loss represents roughly five percent of the country's approximately 63 gigawatts of installed nuclear capacity, the backbone of a power system that typically derives around two-thirds of its electricity from atomic energy.
The disruptions began on Monday. Two of the affected reactors are scheduled to resume operation by Wednesday night, while the remaining two — which together account for 1.8 gigawatts of capacity — could remain offline until the end of the week, according to regulatory filings.
Parts of France are forecast to see temperatures approach 40°C in the coming days, as Europe contends with its fifth heat wave of the summer. The prolonged period of extreme heat has affected energy infrastructure across the continent, and because France's grid is interconnected with neighboring countries through the European power network, significant output losses can ripple into markets in Germany, Belgium, Spain, and Italy.
Unusually warm waters off the coast of France can trigger rapid increases in jellyfish populations, a phenomenon known as a "bloom." Coastal nuclear plants such as Gravelines rely on pumping stations that draw in seawater to cool reactors, making them vulnerable to ingress by marine organisms.
EDF is also facing significant output restrictions at inland nuclear sites situated along rivers, where elevated water temperatures mean that the water can no longer cool reactors effectively without risking environmental damage to aquatic ecosystems.
The Gravelines facility, located on France's northern coast near Dunkirk, is among the largest nuclear power stations in the world by installed capacity. The plant experienced a similar disruption last year, when swarms of jellyfish clogged its filter drums. The recurrence underscores a broader challenge for nuclear operators across Europe, as warming seas and rivers increase the frequency of climate-related disruptions to cooling systems designed for historical temperature norms.
France operates the second-largest nuclear fleet in the world, making EDF's operational challenges a significant factor in European power markets during periods of peak demand.
