Nuclear-power stocks fell after regulators voted against a deal between Amazon and Talen Energy.The deal would permit a Talen nuclear plant to provide an Amazon data center with extra power.Nuclear stocks have surged this year as AI data centers boost energy demand.

Nuclear-power stocks slumped on Monday after US regulators barred a plant from supplying extra power to an Amazon data center.

The Federal Energy Regulatory Commission rejected the deal between Amazon and Talen Energy late last week. According to FERC Commissioner Mark Christie, approving the proposal would spark consequences for grid reliability and consumer costs.

Talen dropped as much as 8.6% on Monday, unleashing a broader downturn in the nuclear power sector. Vistra slid 6.7% at intraday lows, while Constellation Energy tanked 13%.

These firms have gained sharply as AI data centers have driven US power demand to new heights. In recent months, tech companies have come to embrace nuclear power to run these centers, fueling underlying equities.

Both Vistra and Constellation are among the top S&P 500 performers this year. In a similar fashion to Talen, Constellation reached a 20-year deal with Microsoft to power its data center in

But the FERC’s decision sets a precedent that could challenge nuclear data center deals.

“FERC’s decision will have a chilling effect on economic development in states such as Pennsylvania, Ohio, and New Jersey,” Talen said in a statement.

According to Bloomberg, the firm was already paid $650 million in March by Amazon Web Services for a data center campus next to the Pennsylvania plant at issue. AWS also signed a long-term deal to purchase power from the plant.

Other nuclear equities also suffered on Monday, with the Sam Altman-backed firm Oklo and Nano Nuclear Energy both falling by double-digits.