A swarm of jellyfish have caused four reactors at a French nuclear power plant to switch off. -AAP Image
Four reactors at France's largest nuclear power station in Gravelines on the English Channel were temporarily shut down due to a swarm of jellyfish in the plant's water pumping stations.
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There was a "massive and unpredictable" accumulation of jellyfish in the filter drums of the pumping stations located in the non-nuclear part of the plant, operator Électricité de France (EDF) said in a statement.
Three units were automatically shut down on Sunday night followed by the fourth early on Monday, however the safety of the plant was not at risk, EDF said.
The nuclear plant in northern France is cooled from a canal connected to the North Sea. Its six units produce 900 megawatts of power each, or 5.4 gigawatts in total.
An EDF spokeswoman said said energy production had been temporarily halted because maintenance work on the other two units.
However, the company spokeswoman emphasised there was no threat to power supplies because other plants could compensate for the outage.
The type of jellyfish involved is being investigated, the spokeswoman added.
Jellyfish have also caused problems at a nuclear power plant in Sweden in the past.
About 70 per cent of France's electricity comes from nuclear energy, according to the World Nuclear Association (WNA).
