Talen Energy (TLN) and Amazon (AMZN) shares fell over 2% and 1%, respectively, on Monday. The decline came after the U.S. Federal Energy Regulatory Commission (FERC) denied a request to increase the power supply from TLN’s Susquehanna nuclear plant to AMZN’s data center campus.

Big tech companies need lots of electricity for their data centers, which are processing increasingly complex artificial intelligence applications.

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.