The U.S. Nuclear Regulatory Commission is expected to approve licenses to build two new nuclear reactors Thursday, the first approvals in over 30 years.

The reactors are being built in Georgia by a consortium of utilities led by Southern Co. They will be sited at the Vogtle nuclear power plant complex, about 170 miles east of Atlanta. The plant already houses two older reactors.

Spokespeople for Southern Co. and the NRC were quiet on the matter Wednesday ahead of the vote set for Thursday at 12 PM ET. If approved, NRC staff would likely issue a construction and operating license within the next few days.

Although new nuclear reactors have been built in this country within the last couple of decades -- the last one started operation in 1996 -- the NRC hasn't issued a license to build a new reactor since 1978, a year before the Three Mile Island accident in Pennsylvania. The reactors that have opened in the last decades were approved before 1978.

The combination of the Three Mile Island incident and the high costs of nuclear power turned many utilities away from the technology.

There are currently 104 operating nuclear reactors at 64 plants across the country that provide the nation with roughly 20% of its power. Half are over 30 years old.

The utilities building the new Vogtle reactors submitted their application seven years ago. Prep-work at the site has been under way for some time, but the actual reactors can't be built until NRC issues the final license.

The new reactors are a Westinghouse design called the AP 1000. Together they are expected to cost $14 billion and provide 2200 megawatts of power, according to a spokesman for Southern Co. That's enough to power 1 million homes.

The plants are being built with the help of a conditional $8.3 billion loan guarantee from the Department of Energy. The loan guarantee is part of DOE's broader loan program that has been criticized for backing companies like Solyndra, the bankrupt maker of solar panels.

The Southern spokesman said the loan guarantee, combined with other regulatory measures, enable the project to receive cheaper financing that will ultimately save ratepayers $1 billion.

The first reactor is expected to come online in 2016 and the second one in 2017, according to Southern Co.

The AP 1000 is the newest NRC-approved nuclear reactor. This would be the first one built in the United States, although four are already under construction in China, said Scott Shaw, a Westinghouse spokesman.

Critics have said the containment walls of the AP 1000 aren't strong enough to withstand a terrorist attack, but Shaw says they were redesigned after September 11, 2001 and have held up during simulations.

He also said the design's passive cooling system makes it much safer than older designs. The AP 1000 uses gravity and condensation -- not electricity -- to cool the fuel rods.

It was the loss of electric power that led to the meltdown of Japan's Fukushima Daiichi reactors following the tsunami in 2011.

Still, a coalition of nine mostly regional environmental groups say the current design is not safe. They are asking the NRC to delay its decision Thursday until they can file a challenge in federal court.