A huge cluster of jellyfish forced the Oskarshamn nuclear plant in Sweden to shut down on 29 September 2013. The jellyfish clogged the pipes that bring in cooling water. It took two days to fix the problem.
Jellyfish have caused problems at many nuclear plants around the world, as have fish and other aquatic life. A few examples:
- In 2005, one reactor at Oskarshamn was temporarily shut down due to jellyfish.
- EDF Energy manually shut down the Torness nuclear power plant in Scotland in mid-2011 because jellyfish were obstructing the cooling water intake filters. (In May 2013, the two Torness reactors were temporarily shut down because seaweed blocked the water intake pipe.)
- In 2012 a reactor at the Diablo Canyon nuclear power plant in California was shut down after sea salp − a gelatinous, jellyfish-like organism − clogged water intake pipes.
- In July 2009 a reactor in Japan was forced to temporarily shut down due to infiltration of swarms of jellyfish near the plant. Jellyfish disrupted operation of the Shimane nuclear plant in Japan in 1997 and 2011.
Marine biologists warn the jellyfish phenomenon could become more common. Lene Moller, a researcher at the Swedish Institute for the Marine Environment, said: "It's true that there seems to be more and more of these extreme cases of blooming jellyfish. But it's very difficult to say if there are more jellyfish, because there is no historical data."
Increased fishing of jellyfish predators and global warming are contributing to higher jellyfish populations. Monty Graham, co-author of a study on jellyfish blooms published in the Proceedings of the National Academy of Sciences in June 2011, blames global warming, overfishing, and the nitrification of oceans through fertiliser run-off.
 Gary Peach, 1 Oct 2013, 'Wave of jellyfish shuts down Swedish nuke reactor', http://phys.org/news/2013-10-jellyfish-swedish-nuke-reactor.html
 Aaron Larson, 1 Oct 2013, 'Nuclear Plant Shut Down Due to Jellyfish', www.powermag.com/nuclear-plant-shut-down-due-to-jellyfish/
 'Fire and Jellyfish Threaten Plant Operations', 07/06/2011, POWERnews, www.powermag.com/fire-and-jellyfish-threaten-plant-operations/
 Reuters, 24 May 2013, 'Seaweed stops Scottish EDF nuclear plant', http://uk.reuters.com/article/2013/05/24/uk-edf-britain-seaweed-idUKBRE9...
 Monami Thakur, 9 July 2011, 'Millions of Jellyfish Invade Nuclear Reactors in Japan, Israel', www.ibtimes.com/millions-jellyfish-invade-nuclear-reactors-japan-israel-...
 Reuters, 24 June 2011, 'Jellyfish back off at Japan nuclear power plant', http://in.reuters.com/article/2011/06/24/idINIndia-57889320110624
 Glenda Kwek, 11 July 2011, 'Jellyfish force shutdown of power plants', www.theage.com.au/environment/jellyfish-force-shutdown-of-power-plants-2...