NukesJellyfish attack shuts down Swedish nuke

The Oskarshamn nuclear plant in southeastern Sweden, one of the world’s largest nuclear power plants, was forced to shut down when it was attacked by a large cluster of jellyfish.

SFGate reports thaton Sunday, operators of the plant had to scramble reactor number three after a cluster of jellyfish, weighing several tons, clogged the cooling pipes which carry water to keep the core of the reactor cool.

The 1,400 megawatt reactor is the world’s largest boiling-water reactor (BWR). Japan’s Fukushima Daiichi plant was also a BWR.

Anders Osterberg, a spokesman for OKG, the plant operator, said that early yesterday (Tuesday) the plant’s engineers were finally able to remove the last of the jellyfish from the cooling pipes and restart the reactor.

SF Gate notes that experts note that jellyfish is a problem with which nuclear plant operators are familiar. In California last year, the Diablo Canyon nuclear plant was forced to shut its reactor two after gobs of sea salp — a gelatinous, jellyfish-like organism — clogged intake pipes. In 2005, the first unit at Oskarshamn had to be turned off after jellyfish clogged its cooling pipes.

Marine biologists are not surprised to see these jellyfish shutdowns.

“It’s true that there seems to be more and more of these extreme cases of blooming jellyfish,” said Lene Moller, a researcher at the Swedish Institute for the Marine Environment. “But it’s very difficult to say if there are more jellyfish, because there is no historical data.”

The species that caused the problem at Oskarshamn is known as the common moon jellyfish.

“It’s one of the species that can bloom in extreme areas that … are overfished or have bad conditions,” said Moller. “The moon jelly likes these types of waters. They don’t care if there are algae blooms, they don’t care if the oxygen concentration is low. The fish leave … and (the moon jelly) can really take over the ecosystem.”