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Jellyfish-Like Creatures Force Shutdown of Nuclear Reactor

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Sea creatures have been clogging up the water intake screens at one of the units at California's Diablo Canyon nuclear power plant, located in Avila Beach in San Luis Obispo.

Now these "small jellyfish-like animal[s] called a sea salp" have forced Unit 2 to be taken offline, according to San Luis Obispo's Tribune.

The unit, a 1,118 MWe pressurized water reactor supplied by Westinghouse, draws its cooling water from the Pacific, per Wikipedia. That water is used only once, is not recirculated, and gets sent back into the ocean at a slightly warmer temperature than when it was taken in.

The salp began to reach the screens earlier this week. More from the Tribune:

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The event began Tuesday when southerly winds began blowing the salps into the plant’s cooling water intake cove. Plant operators noticed differences in water pressure at the intake structure, indicating the salps were beginning to clog the rolling screens in front of the intake, said Ed Halpin, PG&E’s chief nuclear officer.

Speaking of clogged, that's what can happen to a salp itself. "[B]ecause the salps have to pull the water through their bodies to both eat and move, when they are in very dense populations of phytoplankton they can actually become clogged with their food source and sink," explains It's Nature.

They are typically 2- to 3-inches long, and join together to form rope-like strands.

Diablo Canyon is now the second nuclear power plant in California to have gone offline; San Onofre in Orange County in SoCal has been down for a few months following the discovery of a leak. This isn't what is happening in SLO, though: "Diablo Canyon’s steam generators are designed differently, manufactured by a different company and are not experiencing the same problems, plant spokesman Tom Cuddy said."

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The unit's shutdown is not expected to affect California's power grid.