What is HALEU (high-assay low-enriched uranium)?

How it works

Natural uranium is about 0.7% uranium-235 (U-235), the fissile isotope that sustains a chain reaction. Enrichment raises that share. Traditional reactor fuel is enriched to between 3% and 5%, according to the U.S. Nuclear Regulatory Commission (NRC). It puts HALEU between 5% and 20%. Uranium at 20% or more is classed as high-enriched uranium. The federal statute on advanced nuclear fuel availability uses a matching definition: uranium with an assay above 5.0 and below 20.0 weight percent U-235.

The NRC describes two ways to make HALEU: enriching uranium further or downblending more highly enriched uranium with lower-enriched material. It says its licensees enrich with gas centrifuges.

Why it matters

In an explainer dated December 2024, the Department of Energy (DOE) says most U.S. advanced reactors require HALEU. It says HALEU allows more compact designs with higher power output for their size and longer operating cycles. DOE estimates domestic demand could reach 50 metric tons a year by 2035. The NRC adds that fuel enriched to between 5% and 10% could also be used in existing light water reactors, subject to its regulations.

Supply has been limited. IEEE Spectrum reported in November 2023 that only two companies worldwide could produce HALEU. It named Centrus Energy, at its plant in Piketon, Ohio, and Russia's state-owned Tenex. It also reported that TerraPower said in December 2022 it was delaying its Natrium demonstration reactor by two years for lack of the fuel.

Where things stand in 2026

The NRC's HALEU page, last reviewed or updated on September 14, 2026, says the material is not used in U.S. commercial power reactors. It names two licensees that may produce HALEU: Centrus, at enrichments up to 19.75%, and Louisiana Energy Services, up to 5.5%.

On January 5, 2026, DOE announced $2.7 billion in enrichment task orders over ten years. Those included $900 million each to American Centrifuge Operating and General Matter to build domestic HALEU enrichment capacity. Nuclear Newswire reported in July 2026 that Centrus signed a contract finalizing a $900 million DOE task order to expand HALEU production at its American Centrifuge Plant in Piketon. Centrus said it had made more than 1,900 kilograms of HALEU, as uranium hexafluoride, under an earlier DOE demonstration contract. The report said Centrus plans an initial 12 metric tons of annual HALEU capacity. It said Centrus expects new commercial capacity to start by 2029.