Jellyfish Invasion Forces EON to Shut Down Swedish Nuclear Plant

EON SE shut down Sweden’s biggest nuclear power plant after a swarm of jellyfish made its way into a cooling water inlet at the reactor on the Baltic coast.

The 1,400 megawatt Oskarshamn-3 unit, located about 340 kilometers (211 miles) south of Stockholm, accounts for 5 percent of Sweden’s power supply, Anders Oesterberg, a spokesman for EON, said by e-mail today.

“This situation is caused by a huge amount of jellyfish, just one is definitely not enough to cause problems,” Oesterberg said from Oskarshamn, Sweden. “The last time this happened was in August 2005, when we had to shut down Oskarshamn-1 because of a jellyfish invasion.”

Oskarshamn-3 was halted on Sept. 8 for maintenance and was scheduled to resume output Sept. 27, according to a company filing. EON, Germany’s biggest utility, owns 55 percent of the plant, which was commissioned in 1985. Fortum Oyj (FUM1V) of Finland owns the rest.

More information on the plant stoppage is expected later today, according to an EON filing with the Nord Pool Spot exchange in Oslo.

The jellyfish are part of the genus Aurelia, according to Oesterberg. Known as moon jellyfish, they have pale translucent bodies, are found mainly in coastal areas in Europe and North America and may grow as large as 40 centimeters in diameter, according to the online edition of the Encyclopaedia Britannica.

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To contact the editor responsible for this story: Lars Paulsson at

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