Jellyfish swarm forces shutdown of three French nuclear reactors

Électricité de France shut down three reactors at the Gravelines nuclear power station late on Monday after a massive jellyfish swarm entered the facility ^[1].

The incident highlights the vulnerability of critical energy infrastructure to biological surges triggered by environmental shifts. Because nuclear plants rely on massive volumes of water for cooling, organic blockages can force immediate shutdowns to prevent overheating.

The Gravelines plant, located in the Nord department of northern France, is the largest nuclear power station in Western Europe ^[1]. The swarm forced the closure of three of the six total reactors at the site ^[1], ^[2].

EDF took the measure to protect the plant's cooling systems from the influx of jellyfish ^[4]. These systems pull in seawater to regulate reactor temperatures, but a high density of jellyfish can clog the intake filters, effectively choking the plant's ability to cool its cores.

Experts link the surge in jellyfish populations to a combination of human-driven environmental factors. These include the effects of over-fishing, which removes natural jellyfish predators, and the prevalence of plastic pollution in the ocean ^[2].

Additionally, warming seas caused by climate change have created more favorable breeding conditions for these organisms ^[2], ^[4]. This convergence of factors has led to more frequent and intense blooms in the North Sea and surrounding coastal waters.

While the plant remains operational with its other three reactors, the event underscores a growing tension between industrial requirements and changing marine ecosystems. The facility must now manage the clearance of the organic debris before the halted reactors can safely return to service ^[1].