Nuclear Power Is the New A.I. Trade. What Could Possibly Go Wrong?

Want to make a wager on the future of artificial intelligence? Nvidia is the obvious bet. It designs the chips and software that make A.I. run, is the stock market favorite and has gained 150 percent this year alone.

But some stock traders have found a less obvious, backdoor choice: utility shares, specifically those of companies that own nuclear power plants.

Two such companies — Constellation Energy and Vistra — were the top performers in the S&P 500 in September through Thursday, with returns of more than 30 percent. Shares of Constellation Energy, the biggest nuclear plant operator in the United States, surged when it signed a deal on Sept. 20 to supply Microsoft’s burgeoning A.I. data centers with energy from the Three Mile Island nuclear power plant near Harrisburg, Pa.

If you were a consumer of news in 1979, or are aware of the history of nuclear power, you will know that Three Mile Island was the site of the worst nuclear disaster in U.S. history. Now, because of A.I. energy demand, the utility intends to reopen an undamaged part of Three Mile Island that was mothballed five years ago and change its name, to the less evocative Crane Clean Energy Center.

Vistra says it, too, has been in talks with several A.I. operators. And the Constellation deal with Microsoft followed an A.I.-nuclear power agreement in March involving Talen Energy and Amazon. Talen agreed to sell Amazon large quantities of electricity from the Susquehanna Steam Electric Station — a nuclear plant near Berwick, Pa., in which the utility has a 90 percent ownership stake.

Consider these stock returns for the year, including dividends, through Thursday:

• The S&P 500 stock index, 21 percent.

• Constellation Energy, 121 percent.

• Vistra, 199 percent.

• Talen Energy, 178 percent.

Other utilities have gotten a boost from A.I., too, but generally not as spectacularly as these companies.