President Donald Trump said he's ordered two nuclear submarines to move in the "appropriate regions" in response to recent comments from Russia's Dmitry Medvedev.
Facing possible electricity shortages, California Gov. Gavin Newsom is considering keeping the state's last nuclear power plant online beyond its planned closing in 2025.
This week, Russian forces seized control of the defunct Chernobyl nuclear power plant, the site of the 1986 nuclear disaster.
The plant was shut down in 2012 after a radiation leak led to the discovery of extensive damage to hundreds of tubes inside the steam generators. The plant never produced electricity again.
Ontario Power Generation later tweeted that the alert "was sent in error. There is no danger to the public or environment."
Controversy surrounds the future of the shuttered San Onofre nuclear power plant amid serious environmental and safety concerns.