moon-jellyfishA Swedish nuclear reactor is close to reopening after it was clogged by an unlikely enemy- jellyfish. Officials from the Oskarshamn nuclear plant in southeastern Sweden confirmed a large invasion of Aurelia aurita, or moon jellyfish, plugged the cooling water intake pipes Sunday. The invasion forced operators to shut down its reactor number three, one of the world’s largest nuclear reactors.

The plant’s reactor number three is a 1,400-megawatt boiling-water reactor on the Baltic Sea. According to the New York Times, the jellyfish entered the pipes 60 feet below the surface of the sea and never made it past the filtration system. The plant said they were working to reverse the water flow to remove the jellyfish. Tuesday, Anders Osterberg, a spokesman for the operator, Oskarshamns Kraftgrupp AB, told Bloomberg, “The aim is to slowly start a couple of the cooling water pumps in order to drain the inlet pond of jellyfish and see that they are all distributed back to the sea. When the amount of jellyfish is reduced to an acceptable level, we will be able to restart production.”

Strangely, this is not the first time jellyfish have shut down a nuclear reactor. The Oskarshamn nuclear plant had an identical incident in 2005, in which their nuclear reactor number one was forced to shut down. Also, the U.S., has had two shut downs within the last five years. A massive invasion forced the Diablo Canyon 2 reactor in California to temporarily close in October 2008, when jellyfish clogged water screens. In August 2011, a huge swarm of moon jellyfish clogged a cooling canal at the St. Lucie Nuclear Plant in Florida, forcing an unplanned shut down.

Despite more knowledge of the issue, there is no clear way to prevent a future occurrence. According to National Geographic, the main cause in the growing population of moon jellyfish is overfishing. Moon jellyfish have few natural predators, which are often overfished, allowing the jellyfish to over populate. The jellyfish are also able to withstand increasing ocean acidity as other marine species succumb to it. Lene Moller, a researcher at the Swedish Institute for the Marine Environment, said, “It’s one of the species that can bloom in extreme areas that . . . are overfished or have bad conditions. 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.”

For now, Oskarshamn is going to remain hopeful this is the last of the jellyfish invasions. “We hope we have solved the problem regarding the jellyfish, but we are not sure because they can come back,” Mr. Osterberg said to the New York Times. He did assure that no jellyfish were boiled, and if any were injured it was due to pressure, not over-heating. Reactor number three is due to start operating as usual by October 4.

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  • homayoun Sabbaghzadeh

    Dear Sirs/Madams ;
    I faced to this problem near 5 years ago in one of my country’s Power Plant and found the best
    solution to solve the Jellyfish attack to Inlet of Cooling System in Power Plant which cause to
    shut down and closing the whole plant . By this methods the Cooling System Inlet Protected from Jellyfish’s attack and now the power plant work normally . If need to have discussion about I will be
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    Best Regards
    Dr. Homayoun Sabbaghzadeh
    Researcher & Managing Director of R&D Company
    [email protected]