fuel challenges facing advanced reactors

Published: July 2026

High-assay low-enriched uranium, or HALEU, is emerging as one of the most important materials in the future of nuclear energy. Defined as uranium enriched to more than 5% and less than 20% uranium-235, HALEU contains a higher concentration of fissile material than the low-enriched uranium used in most of today’s commercial nuclear reactors. That higher energy density allows many advanced reactors to be smaller, operate for longer periods between refueling, and achieve improved performance compared with current reactor technologies, according to the U.S. Department of Energy and the International Atomic Energy Agency.

For the United States, building a domestic HALEU supply is not simply a fuel-cycle issue. It is a prerequisite for deploying many of the advanced reactors being developed to support energy security, industrial growth and emissions reduction. The DOE says most advanced reactor designs require HALEU, and that gaps in supply could delay deployment. The agency also notes that HALEU is not currently available from domestic suppliers at commercial scale, creating a bottleneck for reactor developers, fuel fabricators, utilities and investors.

Read more:

• Energy.gov: HALEU Availability Program
• Energy.gov: U.S. Department of Energy HALEU Consortium

The need is especially important because advanced reactors and small modular reactors, or SMRs, are increasingly viewed as tools for meeting energy and environmental goals. SMRs are designed to produce electricity in smaller increments than traditional gigawatt-scale nuclear plants, with potential applications that include power generation, process heat, desalination and other industrial uses. DOE describes advanced SMRs as part of its goal to develop safe, clean and affordable nuclear power options, citing their smaller physical footprints, reduced capital investment, flexible siting and ability to add power incrementally.

Those characteristics matter as electricity demand rises from data centers, artificial intelligence, electrification and industrial growth. Unlike wind and solar, nuclear reactors can provide around-the-clock power without direct carbon emissions during operation. SMRs are being promoted as a way to deliver reliable, carbon-free power closer to industrial users, remote communities, retiring coal plant sites and high-demand grid nodes. DOE has said SMRs can help provide clean, reliable baseload power while supporting grid resilience, energy independence and domestic deployment of U.S.-based reactor technologies.

Read more:

• Energy.gov: Advanced Small Modular Reactors (SMRs)
• DOE Office of Clean Energy Demonstrations: DOE Announces $900 Million to Accelerate the Deployment of Next-Generation Light-Water Small Modular Reactors

HALEU is central to that vision because many advanced reactor designs are not optimized for traditional reactor fuel enriched below 5%. Higher-assay fuel can enable smaller core designs, longer operating cycles and greater fuel efficiency. The IAEA has similarly noted that HALEU could enable smaller reactor designs, longer operating cycles and increased efficiencies, while warning that sufficient supply will be critical for SMR deployment.

Read more:

• IAEA.org: Fuelling the Future: Building Fuel Supply Chains for SMRs and Advanced Reactors

The supply challenge is practical and strategic. Historically, the commercial nuclear fuel cycle was built around uranium enriched up to about 5% U-235 for conventional light-water reactors. HALEU requires additional enrichment capability, deconversion services, fabrication capacity, transportation packages, licensing pathways and criticality safety data. The World Nuclear Association notes that HALEU is not yet widely available commercially and that building a supply chain will require specific fuel-cycle infrastructure, new or modified regulations, transportation solutions and significant capital investment.

See also:

• Oak Ridge National Laboratory: Supporting HALEU fuel cycle availability for domestic research, demonstration, and commercial deployment

Domestic supply also reduces geopolitical risk. The IAEA has reported that Russia has been the only country with commercial-scale HALEU manufacturing capacity, while the World Nuclear Association notes that Russia and China have infrastructure to produce HALEU at scale. For U.S. advanced reactor developers, dependence on foreign HALEU could expose projects to export restrictions, sanctions, transportation delays, contract uncertainty and national security concerns.

The federal government has responded by creating programs intended to jump-start the market. The Energy Act of 2020 directed DOE to establish the HALEU Availability Program to ensure access to HALEU for civilian domestic research, development, demonstration and commercial use. DOE says the program will acquire HALEU through purchase agreements with domestic industry partners and produce limited initial amounts from federal assets, with the goal of encouraging private investment and eventually removing the government’s role as an initial supplier.

That early government role is important because HALEU faces a classic chicken-and-egg problem. Reactor developers need fuel availability to finalize designs, secure customers and reach licensing milestones. Fuel suppliers need bankable demand before investing in enrichment, deconversion and fabrication infrastructure. DOE’s HALEU Consortium was created to help address that gap by collecting demand estimates, supporting demonstration projects and identifying opportunities to improve supply-chain reliability.

The stakes extend beyond individual reactor projects. Idaho National Laboratory’s analysis of HALEU requirements evaluated advanced reactor fuel needs under a scenario consistent with achieving economywide net-zero emissions by 2050. In that scenario, nuclear capacity increased significantly by midcentury, with advanced reactors representing part of the future generation mix.

A domestic HALEU supply chain would not guarantee advanced reactor deployment. Developers still must prove cost, licensing, construction and operating performance. But without reliable HALEU access, many advanced reactors could be delayed before they ever reach the grid. For SMRs to help meet U.S. energy, industrial and environmental goals, fuel availability must advance alongside reactor design. In that sense, HALEU is more than a material input. It is enabling infrastructure for the next generation of nuclear power.