The U.S. military gave us the bones of the internet and the beginning of civilian nuclear power. Will the Defense Department also lead the way on the much-ballyhooed arrival of advanced reactors?
The Pentagon is hip-deep in plans for, not a small, but a tiny, mobile nuke, a 1-5 MW high temperature gas reactor that can be trucked from site to site, or moved by rail, sea, and even, with some limits, by air. It’s called Project Pele. “Pele” is the name of the Hawaiian goddess who created the island chain, and of volcanoes and fire. (The project was not named for the legendary Brazilian soccer star Edson Arantes do Nascimento, aka Pele).
In 2016, the Defense Science Board concluded that current electric energy technology for small, often forward, military bases, mostly diesel generation, was a problem. In its 2022 final environmental impact statement. DOD’s Strategic Capabilities Office described the problem: “Inherent dangers, logistical complexities, and costs of sustaining power demands using diesel generators at U.S. Military Forward Operating Bases, Remote Operating Bases, and Expeditionary Bases constrain operations and fundamental strategic planning. Technologies under development, such as unmanned aerial vehicles, new radar systems, new weapon systems, and electrifying the non-tactical vehicle fleet, will require even greater energy demands.”
The Pentagon decided nuclear was the way to go, and Congress initially appropriated funds for a design competition among BWX Technologies ($13.5 million), Westinghouse Government Services ($11.95 million), and X-energy ($14.3 million). In June 2022, DOD awarded Lynchburg, Va., based BWXT (a Babcock & Wilcox corporate spinoff designed to work specifically on nuclear) some $300 million as the prime contractor.
At a recent American Nuclear Society video conference, BWXT’s Joe Miller said, “We understand in the weeds-level of detail” the challenges to design, build, and test the microreactors. According to a BWXT press release, “The transportable design consists of multiple modules that contain the microreactor’s components in 20-foot long, ISO-compliant CONEX shipping containers.”
There is also a vision for the portable reactors beyond military use. In it’s press release, BWXT said, “Transportable microreactors deliver clean, zero-carbon energy where and when it is needed in a variety of austere conditions for not only the DoD, but also potential commercial applications for disaster response and recovery, power generation at remote locations, and deep decarbonization initiatives.”
BWXT added, “The entire reactor system is designed to be assembled on-site and operational within 72 hours. Shut down, cool down, disconnection and removal for transport is designed to occur in less than seven days.”
Jeff Waksman, the DOD leader on the project, told the ANS meeting that the Energy Department, not the U.S. Nuclear Regulatory Commission, will regulate Project Pele, but the project is collaborating with the NRC. In a May 2022 Waksman paper on the project, he wrote, “DOE is providing reactor safety oversight and authorization, and through an interagency agreement is providing an extension of Price-Anderson nuclear indemnification.” He added, “NRC is participating in a licensing modernization approach to transportation of reactors.”
There may be commercial spinoffs in the future. Waksman said there is a “long history where DOD developed tech that then becomes commercial. We want to build reactors that can have commercial spinoff, get enough coming off the line to be cost competitive.”
A key to the project is the TRISO (Tri-structural Isotropic particle) fuel, which DOE describes: “Each TRISO particle is made up of a uranium, carbon and oxygen fuel kernel. The kernel is encapsulated by three layers of carbon- and ceramic-based materials that prevent the release of radioactive fission products. The particles are incredibly small (about the size of a poppy seed) and very robust. They can be fabricated into cylindrical pellets or billiard ball-sized spheres called ‘pebbles’ for use in either high temperature gas or molten salt-cooled reactors.”
The graphite surrounding the uranium in the fuel is also the moderator, slowing neutrons to facilitate the fission reaction. The gas coolant is inert helium.
The fuel for the Pele reactors will be “high-assay, low-enriched uranium,” or HALEU. It will come from DOE’s inventory of weapons grade uranium, converted from metal into uranium oxide and then “downblended” (can we call it uranium “impoverishment”?) to HALEU, which is typically 7% to 20% fissionable U235.
BWXT has built a 170,000 square foot factory for work on both Pele and NASA’s DRACO space reactor. BWXT’s Miller says they will build the Pele reactors entirely on the factory floor, shipping them in modules to the DOD site, where they will be connected to form a complete generating station.
A fuel load is expected to last some three years. What happens then, with the waste and refueling? DOD’s Waksman said it is “unlikely” the regulators “will ever allow defueling out at site. All the radioactive stuff is in one box. So you ship whole box back, get new box. You don’t want folks messing with fuel on site.” In short, it’s like an auto battery, take out the old, put in the new.
Pele is the Pentagon’s second go-round with tiny reactors, with mixed results. In 1954, the Army began its nuclear power program jointly with the Atomic Energy Commission, developing both stationary and mobile tiny reactors, some eight in all, both boiling and pressurized light-water reactors, used for electric power, heat, or both.
Unfortunately, one of the Army reactors had a tragic history. Built in 1958 and located at the National Reactor Testing Station, now the Idaho National Laboratory, BWR SL-1 generated 200 kW of power and 400 kW of heat. On Jan. 3, 1961, during restart after an 11-day shutdown over the holiday season, as the three-man crew was manually withdrawing the main control rod: the shift supervisor on top of the reactor along with a trainee, the reactor operator manipulating the control rod on the ground.
For still unknown reasons, the control rod was rapidly withdrawn far farther than safe. The reactor then went prompt critical and exploded. The shift supervisor on the top was impaled by the control rod and pinned to the reactor ceiling. The trainee and the reactor operator both died of physical injuries but all three would have been killed by the intense radiation in any case.
The Army cancelled its microreactor nuclear power program in 1977.
–Kennedy Maize