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.

The Federal Energy Regulatory Commission (FERC) rejected an effort Friday to allow an Amazon data center to tap into additional power from a nearby Pennsylvania nuclear plant. The decision could throw a wrench in efforts by large technology companies to secure so-called “behind the meter” power from nuclear plants as they seek to meet

The proposal would have boosted the amount of electricity coming from the Pennsylvania power plant from 300 megawatts to 480 megawatts.

Constellation Energy will continue to pursue deals to develop data centers on the sites of its U.S. power plants, days after federal regulators dealt a blow to the so-called co-located arrangements, company executives said on Monday.

The Federal Energy Regulatory Commission has dealt a blow to plans by e-commerce and technology giant Amazon to build a series of data centers near Talen Energy’s nuclear power plant

The denial of a power agreement tied to Amazon Web Services' nuclear data center campus could slow a potential wave of similar projects across the U.S.

U.S. energy regulators rejected an amended interconnection agreement for an Amazon data center connected directly to a nuclear power plant in Pennsylvania, a filing showed on Friday.

The commission agreed with opponents of the proposal, citing concerns about grid reliability and cost fairness.

Supporting the development of data centers — including providing the enormous amounts of electricity they require — is a matter of national security, a top federal energy regulator said.