One of the largest nuclear power plants in Europe was forced to shut down after some unusual visitors.
Gravelines nuclear power plant in northern France was fully shut down on Monday after a ‘massive and unpredictable’ swarm of jellyfish entered the plant’s pumping stations.
The power station, located between the cities of Dunkirk and Calais, is connected to the North Sea via a canal, which pumps in sea water to cool its reactors.
Its six units produce 900megawatts of power each – but four of them were forced to halt production over the jellyfish invasion.
Data from EDF, which runs the power plant, showed the other two units were already offline for planned maintenance.
The power company said it did not know what species of jellyfish was involved in the shutdown, but that its staff are working to restart the reactor safely.
Reactors 2-4 stopped automatically just before midnight when the filter drums of the pumping stations became packed with the swarm, with reactor 6 going offline several hours later.
EDF said the event did not affect the safety of the facilities, staff or the environment.
It’s understood the filter pumps haven’t been damaged, and that they simply need to be cleaned and the jellyfish removed before the reactors can restart.
This isn’t the first time the Gravelines area has seen swarms of jellyfish, with swarms washing up on beaches there several times in recent years.
The increase is likely due to water temperatures rising thanks to global warming, as well as the introduction of invasive species.
Derek Wright, marine biology consultant with the US National Oceanic and Atmospheric Administration, explained: ‘Jellyfish breed faster when water is warmer, and because areas like the North Sea are becoming warmer, the reproductive window is getting wider and wider.
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‘Jellyfish can also hitch rides on tanker ships, entering the ships’ ballast tank in one port and often getting pumped out into waters halfway across the globe.
‘Everyone talks about nuclear being clean, but we don’t think about the unintended consequences of heat pollution.’
While it’s not known what species of jellyfish was sucked into the Gravelines cooling system, one invasive species known as the Asian Moon jellyfish was first spotted in the North Sea in 2020.
The species, native to the Pacific Northwest, has caused similar problems at nuclear plants in China, Japan and India.
Asian Moon jellyfish are not considered dangerous as their sting is incredibly mild and causes very little harm to humans.
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