The 10 Biggest Nuclear Reactors

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  • Net Capacity: 5,873 megawatts
  • Location: Gyeongsangbuk-do, South Korea
  • Number of Reactors: 6
  • Output (2010): 47,947.308 gigawatt-hours

South Korea gets 32 percent of its electricity from nuclear power -- close to 79 percent of it is generated at Ulchin and Yonggwang (next on our list). But don't be surprised if that statistic changes in the next 10 years. South Korea plans to increase its nuclear energy capacity by 56 percent by 2020. This means more reactors cranking out more power. To say that nuclear power is a strategic priority in South Korea is an understatement.

South Korean power reactors have some of the world's highest capacity factors, averaging 96.5 percent in recent years [source: World Nuclear Association]. This means that, on average, South Korea's reactors operate extremely close to their full capacity, producing 96.5 percent of their potential output over a given period of time. What's responsible for that efficiency? In part, Korean Standard Nuclear Plant (KSNP) design. KSNP is a series of standardization steps that's been developed over the years to optimize nuclear reactor performance and safety. Units 3 and 4 at Ulchin power plant were the first KSNP reactors to be built. During its first cycle of operation, Ulchin's Unit 3 achieved a 103 percent capacity factor and a 100 percent availability factor [source: Power Technology]. That's impressive stuff. By comparison, the reactors at the Gravelines facility, known for its efficient power production, have an average capacity factor of around 88 percent.

On its own, the Ulchin power station generates nearly 34 percent of South Korea's nuclear power, and in 2010 the plant produced enough energy to light up the entire state of Oregon for a year [source: KU Institute for Policy & Social Research].