(Bloomberg) -- NextEra Energy Inc. is seeking permission to run its St. Lucie nuclear plant in Florida until it’s 80 years old, joining other U.S. power providers in a push to preserve the country’s biggest source of clean energy.

The company is asking the Nuclear Regulatory Commission to extend the licenses for the plant’s two reactors for another 20 years, according to a notice Wednesday. Unit 1 was initially licensed in 1976 and has permission to operate through 2036, and Unit 2 was approved in 1983 and can operate through 2043. 

If approved, St. Lucie will be one of a growing number of U.S. nuclear plants set to run for eight decades, the oldest fleet in the world. As more states impose clean-energy mandates, carbon-free nuclear power is going to be a key part of the battle against climate change. Reactors supply about 20% of U.S. electricity and more than half of its clean power. 

NextEra already has approval to operate its Turkey Point plant in Florida for 80 years. Dominion Energy Inc. and Exelon Corp. also plan to run some of their reactors until they reach that age, while Duke Energy Corp. in June said it expects to seek permission to do the same for its entire fleet of 11 reactors.

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