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Spineless attacks on nuclear power plants could increase via The Bulletin of Atomic Scientists

Nuclear power plants increasingly face a new enemy: the humble jellyfish.

These aquatic animals—and algae and other plants—get caught in and block the cooling water intake pipes of nuclear power plants, preventing nuclear reactors from getting the huge amount of water they need every day to cool their reactor cores and associated equipment.

Usually, screens prevent aquatic life and similar debris from being drawn into the power plants’ cooling system. But when sufficiently large volumes of jellyfish or other aquatic life are pulled in, they block the screens, reducing the volume of water coming in and forcing the reactor to shut down.

Jellyfish and algae have assaulted nuclear power plants in the United States, Canada, Scotland, Sweden, Japan, and France. In Scotland alone, two reactors at the country’s Torness power station had to shut down in a single week when the seawater they used as a coolant was inundated with jellyfish. (Because of their tremendous need for cool water, nuclear power plants are often located next to oceans and other naturally occurring large bodies of water.)
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A freak event that keeps recurring. Shutdowns caused by jellyfish have occurred all over the globe. In 2011, the Shimane nuclear power plant in Japan had to shut down due to an influx of jellyfish. The same problem occurred twice at Sweden’s Okarshamns nuclear power plant—home to the world’s largest boiling water reactor—which was forced to shut down because of a bloom of moon jellyfish in 2005, and stop generating again for three days in 2013. Jellyfish have been a problem for decades at California’s Diablo Canyon nuclear power plant. As far back as 1984, jellyfish caused Florida’s St. Lucie plant to shut down; it happened again in 2011—this time with a two-day shut down.

Such supposedly freak events may become even more common in the future, because of degraded environmental conditions that favor jellyfish. The Asian press has reported near-annual swarms of the massive species known as Nomura’s jellyfish (Nemopilema nomurai)—a six-foot diameter, 440-pound species that used to arrive on Japan’s coasts only about once every 40 years. Japan’s Shinichi Ue, a professor of marine science at Hiroshima University, warned in November 2014 that the world will be “in big trouble” if its leaders “fail to get serious about countermeasures against jellyfish.”

For now, the responses to jellyfish fouling of intake channels of nuclear reactors include flushing blocked screens with water or having divers hand-clean the screens.

Algae, too. And jellyfish are not the only problem. Many forms of aquatic life can cause problems with the cooling water intake system at nuclear power plants. Recently, Cladophora—a taxonomic grouping that includes many similar species of green algae—have been of particular concern, causing problems at nuclear reactors along the Great Lakes multiple times.

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