The U.S. Energy Department is throwing its support behind a request by utilities to extend the life of some nuclear power reactors — keeping them in operation for as long as 80 years.

An official with the department, who asked not to be named to discuss its decision-making process, said the agency was conducting research and working with utilities seeking permission from the Nuclear Regulatory Commission to allow reactors built in the 1970s to keep operating to 2050 and beyond.

Already, the utilities Exelon Corp., and Dominion Energy Inc. and NextEra Energy Inc. have said they plan to ask regulators to extend 60-year licenses by 20 years for eight reactors in Virginia, Pennsylvania, and Florida. Requests for as many as 20 more are expected to follow, according to the nuclear industry.