In a bold move against Russia last spring, the U.S. government announced it would ban the import of a key ingredient for American energy: enriched uranium. Without an adequate supply of this potent nuclear fuel, the U.S. cannot realize its vision of a grid built on clean energy.
That’s because the future lies in a new generation of reactors scattered across the country at the community level. Known as small modular reactors (SMRs), each of these facilities will produce enough clean energy to power about 650 homes even in the most remote settings. But since these tiny nuclear reactors rely on a type of fuel that is far stronger than what’s used in today’s reactors—called high-assay low-enriched uranium (HALEU)—the U.S. has no choice but to reimagine how it acquires and processes uranium.
The U.S. Department of Energy (DOE) estimates that HALEU demands could be as high as 50 metric tons per year from 2035 onward. At the moment, Russia controls around 44 percent of the world’s uranium enrichment capacity, according to the U.S Department of Energy. While there are not yet any reactors using HALEU for fuel, there are demonstration-stage SMRs in development that will be critical in proving out the technology.
While the future political climate between the U.S. and Russia is uncertain, history suggests America should shore up its own domestic nuclear fuel supply regardless. In fact, limits on American imports of enriched uranium from Russia date back to the 1990s, according to Ken Petersen, former president of the American Nuclear Society, a for-profit organization based in Illinois that promotes the nuclear engineering field.
“Up until 2013, the Russians eliminated their spent warheads and downblended them into commercial-grade reactor fuel for U.S. reactors,” he explains. “In the late 1990s, a restriction was put on Russia where [it] could only supply 20 percent of the U.S. fuel requirements, and after the war in Ukraine, this became a permanent ban except for a few waivers that are available until 2027 so that the U.S. can build up its capacity.”
If America ever hopes to power its next-generation small modular reactors, it must figure out a way to reliably produce enriched uranium without Russia. And lawmakers have come up with an unorthodox short-term plan to make that happen, scrapping uranium from old nuclear warheads.
Nuclear reactors range from generation 1 from the 1950s and 1960s to generation 4 reactors, which are the advanced HALEU SMR reactors being developed today. Both fuel-burning efficiency and safety levels have improved throughout the generations. Today, there are 94 safe and efficient second- and third-generation nuclear reactors in the U.S., according to Michael Goff, principal deputy assistant secretary for nuclear energy at the Department of Energy’s Office of Nuclear Energy.
Small modular reactors are an attractive replacement, as they have lower upfront costs and can be built to different scales. They’re also similar in size to coal fire plants, so as existing plants are retired, SMRs can be installed in their place, making use of the existing site.
Large corporations in the U.S. are already backing SMR projects. As part of a $500 million deal, Amazon is working with Rockville, Maryland-based X-energy to fund its first reactor in Texas, the companies announced last October. The goal is to bring over 5 gigawatts of power projects online by 2039, which is currently the most ambitious commercial small modular reactor project to date. Google has also announced that it’s teaming up with California-based Kairos Power to deploy multiple reactors, up to 500 megawatts, by 2035.
There are two different types of small modular reactors currently being developed: generation 3+ water-based SMRs and generation 4 advanced SMRs.
Generation 4 SMRs are safer and cheaper to produce. If the reactor overheats, it will shut itself down. Generation 4 SMRs can also reach much higher temperatures than the current fleet of nuclear reactors and water-based SMRs, creating efficiencies in electricity conversion that enable the development of smaller reactors—ones that require more highly enriched uranium fuel.
Enrichment is a chemical process that produces a higher concentration of uranium-235 isotopes per area in a fuel, and is often performed using gas centrifuges, which separate isotopes. There are different grades of uranium depending on the level of enrichment, or concentration, of the uranium-235:
- Low-enriched uranium is below 20 percent enriched, and is used in the current U.S. nuclear fleet
- Highly enriched uranium is concentrated to over 20 percent uranium-235, and is used for nuclear weapons and in other military applications
- High-assay low-enriched uranium is concentrated to between 5 and 19.75 percent uranium-235, and will be used in the next generation of nuclear reactors; it’s seen as the future of U.S. nuclear energy
“This enrichment process is the only way you can generate enough material for the U.S. [nuclear] industry to succeed going forward,” says Jeff Chamberlin, associate assistant deputy administrator for the National Nuclear Security Administration.
Without an established domestic HALEU production supply, the National Nuclear Security Administration is extracting uranium from decommissioned warheads and scrap uranium from old nuclear projects to develop the potent nuclear fuel for small modular reactors. This is an intermittent solution that takes place through downblending.
Downblending is a dilution process that takes highly enriched uranium above 20 percent concentration and blends it with depleted uranium to bring down the enrichment level of the uranium to between 5 and 19.75 percent―safe levels for use as a nuclear fuel. The higher the enrichment, the better the energy efficiency. At 20 percent enrichment—to get it to weapons grade—the uranium enters the category of HEU, so the HALEU cutoff falls just below. Twenty percent is the cutoff point for using uranium in civilian and military applications.
The downblending approach is not new, but is currently necessary. “We’ve been doing this for decades within the NNSA. Material that was put aside and declared surplus to our defense needs, was walled off 20–30 years ago to make sure that we had a supply for our research reactors and medical isotope production,” Chamberlin says. However, the sensitive nature of handling uranium from warheads means that this process is only being performed by government bodies, such as the U.S. Department of Energy and the National Nuclear Security Administration.
Using this process, “the NNSA can make available 1.5 metric tons of HALEU from warhead downblending, and around 6 metric tons if you include the scrap uranium we have lying around,” Chamberlin says. These figures are not estimated annual outputs, but overall totals; when scrap and old warheads are gone, they’re gone. This limited run of HALEU will be made available for the advanced reactor demonstrations, but a larger-scale enrichment process will be a must in the future.
To make HALEU, the Department of Energy is exploring the option of recycling used nuclear fuel from government-owned research reactors using two different chemical processes. The first approach is electrochemical processing. Spent fuel is placed in a high-temperature molten salt chemical bath, and an electrical current separates the highly enriched uranium metal―which can then be cleaned and mixed with low-enriched uranium. According to the DOE, it’s thought that around 10 metric tons of HALEU could be made in total with this approach.
The second approach, still under development, is a hybrid zirconium extraction process that dissolves irradiated fuels in hydrochloric acid gas to remove the aluminum/zirconium cladding materials―the metal casing that protects the nuclear fuel rod from corrosion and stops the release of fission products into the coolant. The uranium is then downblended with low-enriched uranium and passed through a modular solvent extraction system to separate the uranium.
Terrapower, Westinghouse, Radiant, and X-energy―companies all working with Dow Chemical to build a HALEU-based high-temperature gas reactor in Texas―are some of the first companies in line for the downblended HALEU. “A few tons of material have been identified to support those initial tests and first cores, but for second cores, we need new commercial capacity, so that we can be providing enough HALEU for generation 4 reactors,” Goff says.
Both Petersen and Goff have stated that many advanced reactors have been at the chicken-and-egg stage for a while, where no company wants to further develop its reactors before fuel is available, and no one wants to develop fuel for which there are no reactors. “The government has stepped in to bridge that gap,” Petersen says.
There will be a short-term reliance on downblending in the U.S, but this is not a long-term sustainable solution.
The Department of Energy is funding four companies to help spearhead large-scale HALEU enrichment capacity in the U.S. The DOE has already moved forward with an enrichment facility in Piketon, Ohio, with Centrus Energy, which is currently producing 100 kilograms of HALEU per year. Production is expected to increase to 900 kilograms in the coming years.
Goff believes that different reactors―the current generation 2 fleet, generation 3+ water-based SMRs, and generation 4 advanced SMRs―will be required to meet America’s future nuclear energy needs, with the aim of tripling the nuclear capacity in the U.S. from 100 gigawatts to 300 gigawatts. Therefore, increases in both low-enriched uranium and high-assay low-enriched uranium capacity will be vital.
Most of the low-enriched uranium used today in the U.S. is fabricated domestically, and with new advanced reactors set to change the U.S. energy landscape, the hope is that America can also shore up its HALEU enrichment capabilities. It’s going to be a long process that takes time, but it should enable the U.S. to build a more robust supply chain that is not affected by geopolitical events in the coming years.
