Meta announced Tuesday morning that it was paying billions of dollars to keep an Illinois nuclear power plant running through 2047. The social media company will buy all the “clean energy attributes” of Constellation Energy’s Clinton Clean Energy Center, a 1.1 gigawatt nuclear power plant in central Illinois, starting in June 2027.

Electricity will still flow to the local grid, so Meta’s purchase won’t directly power one of its data centers, though the company does have one about two hours north of Clinton in DeKalb. Rather, the deal is a bit of carbon accounting to lower the company’s overall climate impact. It doesn’t reduce emissions on the grid, but prevents them from potentially increasing.

Neither company disclosed exact financial terms, but the multibillion-dollar deal will help Constellation relicense the plant and guarantee a customer for the duration of that license extension.

Big Tech companies — Meta included — have recently become vocal backers of the fission industry. Before the recent boom in data center construction, nuclear reactors had faced a grim future as cheap wind, solar, and natural gas undercut their power-generating costs. But the surge in AI and cloud computing has sent tech companies searching for power, which in turn has led to a string of investments in nuclear startups.

Meta and Constellation have alluded to the deal as a way to save the nuclear power plant from shutdown, though neither said it was at imminent risk of closure.

The power provider initially planned to shut down the Clinton reactor in June 2017 as it faced stiff competition from cheap natural gas, but Illinois legislators stepped in with subsidies that encouraged Constellation to keep the lights on. Those subsidies are set to expire in 2027, and Constellation says the Meta deal will help prevent the closure.

But since 2017, Constellation has not threatened to shut down the Clinton power plant. Instead, in 2022, the company said it would apply to extend the reactor’s operating license through 2047.

Read has asked Constellation about its plans for the Clinton power plant before the Meta deal materialized, and we’ll update this article if we receive a reply. It’s likely that the company would have turned to ratepayers, something Constellation hints at in today’s press release: The deal with Meta “essentially replaces the ZEC (zero-emission credit) program and ensures long-term operations of the plant without ratepayer support.”

Meta and its Big Tech peers have fallen head over heels for nuclear power lately. Meta announced earlier this year that it was soliciting proposals for new nuclear power plants that would generate between 1 and 4 gigawatts of power. Today, the company said it has received over 50 qualified submissions for sites in more than 20 states.

With the Meta deal, Constellation has landed another Big Tech patron for its nuclear fleet. In September, the power provider said that it would restart a reactor at Three Mile Island after Microsoft agreed to buy all the resulting power.