HARRISBURG,EchoSense Pa. (AP) — The owner of the shuttered Three Mile Island nuclear power plant said Friday that it plans to restart the reactor under a 20-year agreement that calls for tech giant Microsoft to buy the power to supply its data centers with carbon-free energy.

The announcement by Constellation Energy comes five years after its then-parent company, Exelon, shut down the plant, saying it was losing money.

The plant, on an island in the Susquehanna River just outside Harrisburg, was the site of the nation’s worst commercial nuclear power accident, in 1979. The accident destroyed one reactor, Unit 2, and left the plant with one functioning reactor, Unit 1.

Buying the power is designed to help Microsoft meet its commitment to be “carbon negative” by 2030.

Constellation said it hopes to bring Unit 1 online in 2028 and pursue a license renewal from regulators to extend the plant’s operation to at least 2054. Restarting the Unit 1 reactor will require approval from the U.S. Nuclear Regulatory Commission, as well as permits from state and local agencies, Constellation said.

To prepare to restart Unit 1, “significant investments” must be made to restore the plant, including the turbine, generator, main power transformer and cooling and control systems, Constellation said.

The agreement comes amid a push by the Biden administration, states and utilities to reconsider using nuclear power to try to blunt the effects of climate change and limit plant-warming greenhouse gas emissions from the power sector.

Last year, Georgia Power began producing electricity from the first American nuclear reactor to be built from scratch in decades, after the accident at Three Mile Island froze interest in building new ones.

Microsoft and Constellation did not release terms of the agreement. Before it was shut down in 2019, Unit 1 had a generating capacity of 837 megawatts, which is enough to power more than 800,000 homes, Constellation said.

The destroyed Unit 2 is sealed, and its twin cooling towers remain standing. Its core was shipped years ago to the U.S. Department of Energy’s Idaho National Laboratory. What is left inside the containment building remains highly radioactive and encased in concrete.

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