Eliminate excess highly enriched uranium through conversion and downblending

Countries with excess stockpiles of highly enriched uranium should eliminate them through
conversion and downblending, and they should publish regular inventory declarations.

• Publish annual declarations of national HEU inventories—even if they have none—to support good accountancy and information-sharing practices
• Strengthen norms against enrichment beyond the threshold needed for civil purposes
• Accelerate downblending programs and designating additional quantities of material as excess available for downblending in the countries with the largest stocks of HEU
• Explore downblending of excess HEU into high-assay low-enriched uranium for use as advanced reactor fuel
• Provide consistent funding for the development of advanced LEU fuels to enable conversion of remaining HEU-fueled research reactors, particularly by Belgium, France, Germany, the United States, and other countries with test reactors and technical expertise in HEU minimization, fuel development, and fuel fabrication
• Develop a neutral, internationally hosted mechanism through the International Atomic Energy Agency to coordinate funding, technical expertise, transport capacity, and material elimination capabilities to simplify access to support for research reactor conversions.

What the Data Show

Stockpiles of highly enriched uranium are increasing in a handful of countries, despite the downward
trend in total global inventories.

Data Details

The most difficult step in making a nuclear weapon is obtaining the weapons-usable nuclear material—as little as 25 kilograms of highly enriched uranium (HEU) is sufficient. Since the 1990s, national and international efforts have tracked and secured HEU stockpiles, removed thousands of kilograms of material that were used to fuel research reactors worldwide, and converted more than 100 of those reactors to use low-enriched uranium (LEU) fuel. HEU minimization is a remarkable global success story for nuclear security, evidenced by the elimination of HEU inventories from 35 countries and Taiwan.

However, momentum on HEU minimization appears to be slowing. The 2026 NTI Index shows that the global HEU inventory decreased by just 6 percent (81,200 kilograms) since 2023. India, Pakistan and Russia are responsible for generating 4,479 kilograms of additional HEU for military purposes, and Iran produced 440 kilograms with no civilian purpose. Belgium’s and Germany’s national stockpiles also increased slightly because of fresh fuel imports for research reactors that are due to be converted to LEU fuels in coming years.

A consistent lack of information sharing about national inventories of HEU creates uncertainty about the rationale for increasing quantities and undermines confidence in responsible stewardship of weapons-usable nuclear materials. The 2026 NTI Index finds that of the 22 countries with weapons-usable nuclear materials, only Australia, France, Germany, and the United Kingdom have made annual public inventory declarations in the past decade. Less frequent declarations diminish the value of information sharing, as they create opportunities to obscure changes in inventories year-over-year and reduce government accountability to declared LEU downblending targets.