TerraPower, backed by Bill Gates, was awarded a $40 million award by the Energy Department in 2016 to pursue the project. (Simon Dawson/Bloomberg)

The Energy Department is participating in major push with electric utility Southern and a company founded by Microsoft founder Bill Gates to develop small nuclear power reactors that are less expensive and more efficient than their much larger cousins.

“Molten salt reactors are getting a reboot,” the Energy Department tweeted late Wednesday, offering a schematic of a battery-like power plant module that “could power America's energy.”

On Thursday, the nuclear industry showed its support for the effort. The new nuclear reactors "could be the energy systems of the future" as companies like TerraPower, backed by Gates, are working to build design and build them, the Nuclear Energy Institute tweeted.

The Department of Energy linked to a detailed description of how its Oak Ridge National Laboratory and other federal labs are teaming up with Southern Company, a big coal utility with several nuclear plants, and Gates’ TerraPower to test and develop a type of reactor that uses liquefied sodium “as both coolant and fuel.”

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These liquid-metal reactors are sometimes referred to as nuclear batteries because they are small, self-contained units, which theoretically can be deployed anywhere, although the version being tested at Oak Ridge appears to be one requiring a permanent structure and housing.

TerraPower was awarded a $40 million award by the Energy Department in 2016 to pursue the project.

Almost 60 years after the first designs for this type of reactor were unveiled, several companies are now starting to develop them as "energy systems of the future," the agency explained.

The Department of Energy has so far invested over $28 million in cost-shared funds for the project to identify and test materials used in the reactor.

Southern Company and TerraPower are currently in the early design phase of testing, supported by Oak Ridge, Idaho National Laboratory, Vanderbilt University and the Electric Power Research Institute, a utility industry-funded research group, to assess the viability of liquid-sodium reactor's for commercial use.

The companies expect to begin testing at a $20 million test facility in 2019, which will help validate the reactor's safety systems for license certification by the Nuclear Regulatory Commission.

After testing, Southern Company and TerraPower plan to develop and license a test reactor before developing a 1,100-megawatt prototype by 2030.

