A huge cluster of jellyfish shut down a considerably large nuclear reactor in Sweden. Operators of the Oskarshamn Nuclear Power Plant had to unjam reactor No. 3 on Sunday after innumerable jellyfish clogged the pipes that bring cool water to the plant's turbines. The pipes had been cleaned and engineers were preparing to re-start the reactor by Tuesday. All three Oskharshamn reactors are boiling-water types. At 1,400 megawatts, the reactor that was shut down is easily the largest boiling-water reactor in the world. Nuclear plants are often built near large bodies of water because they need a constant flow of water to cool their reactors. Marine biologists say they wouldn't be surprised if more these incidents occurred in the future. "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 jellyfish species responsible for the shutdown has been identified as the common moon jellyfish.