The rise of artificial intelligence could breathe new life into the Three Mile Island plant

HARRISBURG, Pa. — The owner of the shuttered Three Mile Island nuclear power plant said Friday it plans to restart the reactor under a 20-year deal that sees tech giant Microsoft buy the electricity needed to power its data centers with carbon-free energy.

Constellation Energy’s announcement comes five years after its then-parent company, Exelon, shut down the plant, saying it was losing money and Pennsylvania lawmakers refused to subsidize it.

The plan to restart Three Mile Island Unit 1 comes amid a nuclear power renaissance, with policymakers increasingly turning to it to shore up a dwindling electricity supply, help stave off the worst effects of climate change and meet growing demand for power generated by data centers.

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

The electricity purchase is designed to help Microsoft meet its commitment to be carbon negative by 2030.

Microsoft declined to say which of its data centers will be powered by the nuclear plant, but the mid-Atlantic power grid stretches from Virginia, a data center for Microsoft and other tech giants, to Ohio, where Microsoft has plans for a new data center complex outside Columbus.

Constellation said it hopes to have Unit 1 online in 2028. Restarting the reactor will require approval from the U.S. Nuclear Regulatory Commission, as well as permits from state and local agencies, Constellation said.

To restart Unit 1, Constellation will spend $1.6 billion to restore equipment including the turbine, generator, main transformer and cooling and control systems. It is not currently seeking state or federal grants to help, it said.

Microsoft and Constellation did not disclose terms of their agreement.

Jacopo Buongiorno, a professor of nuclear science and engineering and director of MIT’s Center for Advanced Nuclear Energy Systems, said Microsoft would likely pay more than the market price for electricity that is both carbon-free and reliable.

Restarting the plant is realistic, but not easy, Buongiorno said.

“It all depends on the condition of the components, the systems,” Buongiorno said.

The process will go smoothly if operations have been well maintained during the shutdown, Buongiorno said. A Constellation spokesman said the plant itself is in excellent condition.

The closest example of a nuclear plant restart is underway in Michigan, Buongiorno said. There, the federal government has promised a $1.5 billion loan to restart the Palisades nuclear plant, which is shutting down in 2022.

The economics of the Constellation-Microsoft deal make sense for both sides, Buongiorno said. Plus, it’s cheaper to restart a nuclear plant than to build one from scratch, he added. The transmission lines, cooling towers, control buildings and concrete containment structures are already intact, he added.

Constellation’s announcement comes after a wave of coal and nuclear plant closures over the past decade as competition from cheap natural gas flooded electricity markets.

The situation has prompted warnings that the United States is facing a power grid reliability crisis. At the same time, demand for data centers run by tech giants like Meta, Amazon, Microsoft and Google to provide cloud computing and digital services such as artificial intelligence systems is growing rapidly.

In the United States, growth in electricity demand is concentrated in states – primarily Virginia and Texas – that are experiencing rapid development of large-scale data centers, the U.S. Energy Information Administration said.

Data centers’ share of U.S. electricity consumption is currently about 4%, and some projections predict it will double by 2030.

The Constellation-Microsoft deal comes as part of a push by the Biden administration, states and utilities to reconsider the use of nuclear power to try to limit greenhouse gas emissions from the power sector that cause warming in power plants.

Last year, Georgia Power began generating electricity from the first U.S. nuclear reactor built in decades, after the Three Mile Island accident froze interest in building new reactors.

Before its closure in 2019, Three Mile Island Unit 1 had a generating capacity of 837 megawatts, enough to power more than 800,000 homes, Constellation said.

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

The late 2022 launch of OpenAI’s ChatGPT, built with help from Microsoft’s data centers, sparked global demand for chatbots and other generative AI products that typically require large amounts of computing power to train and operate.

Google and Microsoft both acknowledged this year that AI’s electricity needs make it harder for them to meet the ambitious climate goals they set before AI’s rise.

“Microsoft, in addition to its own products, also provides the computing resources for OpenAI, which is growing and developing very ambitiously,” said Sasha Luccioni, a researcher at Hugging Face, an artificial intelligence company that has drawn attention to AI’s carbon footprint. “They have to scramble to get all the energy they can to fuel that growth.”

O’Brien reported from Providence, Rhode Island.