WASHINGTON — The Pentagon has selected two companies to move forward with developing small, portable nuclear reactors for military use in the field.

BWXT Advanced Technologies and X-energy were chosen by the department’s Strategic Capabilities Office to continue on with Project Pele, which seeks to develop a reactor of 1- to 5-megawatt output that can last at least three years at full power. In addition, the reactors must be designed to operate within three days of delivery and be safely removed in as few as seven days if needed.

The two companies, along with Westinghouse Government Services, were each given preliminary contracts of less than $15 million in March 2020 to begin design work. The final design is due to the Strategic Capabilities Office in 2022, at which point the Defense Department will make a decision on whether to move forward with testing the systems.

“We are thrilled with the progress our industrial partners have made on their designs,” Jeff Waksman, Project Pele’s program manager, said in a statement. “We are confident that by early 2022 we will have two engineering designs matured to a sufficient state that we will be able to determine suitability for possible construction and testing.”

The Pentagon has long eyed nuclear power as a potential way to reduce both its energy cost and its vulnerability in its dependence on local energy grids. According to a news release, the Defense Department uses “approximately 30 Terawatt-hours of electricity per year and more than 10 million gallons of fuel per day.”

According to an October 2018 technical report by the Nuclear Energy Institute, 90 percent of military installations have “an average annual energy use that can be met by an installed capacity of nuclear power” of 40 MWe (megawatt electrical) or less.

The Biden administration is expected to pursue alternative energy options across the Pentagon, with Defense Secretary Lloyd Austin pledging to lower the department’s carbon footprint and to consider climate impact in strategic decisions. Whether nuclear energy will prove a way forward or not may depend on whether the taboo around nuclear power can be assuaged for local defense communities and members of Congress.

Project Pele is not the only attempt at introducing small nuclear reactors to the Pentagon’s inventory; a second effort is being run through the Office of the Under Secretary of Defense for Acquisition and Sustainment. That effort, ordered in the 2019 National Defense Authorization Act, involves a pilot program aimed at demonstrating the efficacy of a small nuclear reactor in the 2- to 10-MWe range, with initial testing at a Department of Energy site around 2023.

While Project Pele is focused on the potential for deployable nuclear reactors, the acquisition and sustainment effort is focused on domestic military installations, with the goal of being operational by 2027.