Nuclear engineers are making fuel for advanced nuclear reactors known as HALEU, using equipment at Idaho National Laboratory (shown). Idaho National Laboratory
As the world races towards cleaner and more efficient energy solutions, the nuclear power industry is on the brink of a significant transformation. A key player in this new era of nuclear technology is a fuel known as high-assay low-enriched uranium, or HALEU. Once a niche material, HALEU is now at the center of attention for governments, energy companies, and nuclear engineers. But what exactly is HALEU, and why is it so important? Here are four essential things to know about this emerging fuel.
1. What is HALEU?
HALEU, which is pronounced like “Hey, Lou,” is a type of uranium fuel that contains a higher concentration of the isotope uranium-235 (U-235) compared to standard reactor fuel. U-235 is a fissile material, meaning it can sustain a nuclear chain reaction when its nucleus splits, releasing energy in the process.
In its natural state, uranium is composed of about 0.7% U-235, with the majority being the non-fissile isotope uranium-238 (U-238). For use in conventional nuclear power plants, uranium is typically enriched to contain about 3% to 5% U-235. HALEU, however, is enriched to levels between 5% and 20% U-235, placing it between standard reactor-grade uranium and highly enriched uranium (HEU), which is used in nuclear weapons. This unique composition allows HALEU to be used in ways that standard reactor fuel cannot, without the strict regulations associated with HEU.
High-assay low-enriched uranium fuel (shown) is being made at Idaho National Laboratory using spent fuel from a retired nuclear reactor.Idaho National Laboratory
2. Why is HALEU Generating So Much Interest?
The excitement around HALEU stems from its potential to power a new generation of advanced nuclear reactors. These reactors differ from traditional designs in several ways, including size, efficiency, and cooling methods. For instance, some advanced reactors use liquid sodium instead of water for cooling, and they often require fuel with a higher concentration of U-235—hence the need for HALEU.
HALEU allows for smaller, more energy-dense reactor cores, which can reduce construction costs and increase efficiency. Furthermore, HALEU can be utilized in innovative fuel forms, such as metallic fuel or TRISO particles—tiny, coated pellets of uranium that offer enhanced safety features. These advanced reactor designs, supported by the U.S. Department of Energy (DOE), are seen as critical to meeting future energy demands while minimizing environmental impact.
Centrifuges are used to create high-assay low-enriched uranium at a facility in Piketon, Ohio.Centrus Energy Corporation
3. Where Does HALEU Come From?
Despite its growing importance, there is currently no large-scale commercial production of HALEU in the United States. While Russia has been a major supplier, recent U.S. legislation has limited imports of Russian uranium, creating a pressing need for domestic production.
To address this, the U.S. government has been supporting efforts to ramp up HALEU production. One such effort involves Maryland-based Centrus Energy Corp., which has begun producing HALEU at an enrichment facility in Ohio as part of a DOE demonstration project. Additionally, the Idaho National Laboratory is blending preexisting highly enriched uranium with other forms to create HALEU. The goal is to produce enough HALEU to fuel the first wave of advanced reactors, with estimates suggesting that more than 40 metric tons will be needed by 2030.
4. What Are the Concerns Surrounding HALEU?
While HALEU holds great promise, it also raises significant concerns, particularly regarding nuclear security. Historically, HALEU has not been viewed as a material for weapons, but its potential use in advanced reactors has prompted a reevaluation. Scientists have pointed out that HALEU, especially at enrichment levels close to 20%, could be used to create a nuclear weapon with a yield comparable to the bomb dropped on Hiroshima.
Although HALEU is not as easy to weaponize as highly enriched uranium, the amount used in a single reactor could be sufficient to make a crude nuclear weapon. This has led to calls for stricter security measures to prevent the misuse of HALEU, whether by nations without nuclear weapons or by terrorist organizations.
Final Thoughts
As the energy landscape evolves, HALEU represents both an opportunity and a challenge. Its ability to power advanced reactors more efficiently and safely is undeniable, but the associated risks cannot be ignored. As we move forward, ensuring a reliable supply of HALEU while addressing security concerns will be crucial to realizing the full potential of this next-generation nuclear fuel.
This blog post aims to distill complex nuclear science into an accessible and engaging narrative, while also addressing the potential risks and challenges associated with HALEU. Whether you’re a fellow scientist, an energy enthusiast, or simply curious about the future of nuclear power, HALEU is a topic worth following closely.
Citations
R.S. Kemp et al. The weapons potential of high-assay low-enriched uranium. Science. Vol. 384, June 7, 2024, p. 1071. doi: 10.1126/science.ado8693.
