Three reactors at France's Gravelines nuclear power plant were shut down late Monday after a significant swarm of jellyfish disrupted operations. The incident prompted the activation of preventative measures that were implemented following a complete plant outage caused by jellyfish last year.
The plant, situated in northern France, draws cooling water from a canal connected to the North Sea. Reactors 2, 3, and 4 were taken offline due to the jellyfish swarm. Reactor 1 was reduced to 50% capacity as a precautionary measure. Reactor 5 was already undergoing maintenance, and Reactor 6 remained fully operational, according to operator EDF.
Last year's widespread shutdown led EDF to develop new monitoring and trawling techniques. These include installing fixed cameras at intake canals and filter drum screens to detect incoming blockages rapidly. EDF has also collaborated with French fishing and sea rescue organizations to monitor for jellyfish swarms and provide early warnings. Fishing boats were deployed prior to the latest incident to reduce the density of the jellyfish population before they reached the plant.
Jellyfish present at the site are being removed using vacuum trucks, and officials stated that no new jellyfish were arriving. The cleanup was nearing completion, suggesting that the affected reactors could restart soon. EDF confirmed that the incident did not impact the safety of the facility, its personnel, or the environment.
Massive jellyfish swarms can obstruct filtration systems, impeding the flow of cooling water. This necessitates reactor shutdowns to prevent overheating. While such events disrupt power generation, they affect non-nuclear components and activate safety systems designed to shut down reactors before they become a danger.
Scientists suggest that events like these may become more frequent due to factors such as global warming, the proliferation of invasive species, the loss of predator habitats, and overfishing. Separately, EDF is also managing heat-related restrictions at other French nuclear reactors as the country anticipates another heatwave, which could further limit nuclear output.