The fuel cycle: from ore to fuel rod

A fuel assembly arriving at a power plant is the end of a long industrial chain that crosses several countries. Each link has its own companies, its own regulators and its own politics. When the news says "fuel supply," it usually means one specific link, and knowing which one gets you halfway to understanding the problem.

Mining and milling

Uranium ore is mined in open pits, underground mines, or by in situ recovery, where a solution is pumped through an underground ore body and back up, dissolving the uranium without digging. Kazakhstan, the world's largest producer, relies mostly on in situ recovery, as do most active U.S. operations in Wyoming and Texas.

A mill grinds or leaches the ore and produces a concentrate of uranium oxide, U3O8, called yellowcake (it is often more brown than yellow). The leftover rock, called tailings, contains radium that decays into radon gas. The EIA notes tailings are usually stored near the mill under clay barriers covered with soil or rock. The western United States still carries the cost of Cold War era mills that were not handled that way, especially on Navajo Nation land, and that history comes up in any new mining proposal.

Conversion

Enrichment works on a gas, so yellowcake is chemically converted into uranium hexafluoride (UF6), a compound that turns to gas at modest temperatures. In North America there are only a couple of conversion plants, including Honeywell's facility in Metropolis, Illinois, and Cameco's in Ontario. Conversion is a small, quiet step that has caused supply crunches before, because so few plants exist worldwide.

Enrichment

Natural uranium is 0.7 percent U-235. Light water reactors need about 3 to 5 percent. Enrichment separates the slightly lighter U-235 from U-238 by spinning UF6 gas in fast centrifuges, thousands of them linked in cascades. The NRC says gas centrifuges are the method in use today; the old U.S. gaseous diffusion plants in Kentucky and Ohio are closed. The only operating commercial enrichment plant in the United States is Urenco USA's National Enrichment Facility in Eunice, New Mexico, owned by a British, Dutch and German consortium.

Enrichment effort is measured in separative work units, or SWU. You will see prices quoted per SWU. In 2025, EIA says U.S. reactor owners bought about 13 million SWU at an average of $108.70 per SWU.

Enrichment levels

Category	U-235 share	Used for
Depleted uranium	Below 0.7% (often about 0.2 to 0.3%)	Leftover from enrichment; armor, ballast, possible fast reactor fuel
Natural uranium	About 0.7%	CANDU fuel, feed for enrichment
LEU	Up to about 5% (LEU technically means below 20%)	Today's commercial PWRs and BWRs
LEU+	5 to 10%	Proposed for longer fuel cycles in existing plants
HALEU	5 to 20%, often near 19.75%	Natrium, Oklo Aurora, Kairos, X-energy, many microreactors, some research reactors
HEU	20% and above	Naval propulsion, some research reactors; weapons use about 90%

The 20 percent line is an international nonproliferation threshold. Below it, uranium is considered impractical for a weapon. That is why HALEU designs usually stop just under it, at 19.75 percent.

Fuel fabrication

Enriched UF6 is converted back to uranium dioxide powder, pressed into ceramic pellets about the size of a pencil eraser, and baked. Pellets are stacked inside zirconium alloy tubes about 12 feet long. Those rods are bundled into assemblies, a few hundred rods each. Advanced reactors use different forms: TRISO particles packed in pebbles for Kairos and X-energy, and metallic uranium alloy slugs in steel tubes for Natrium.

Where U.S. reactor fuel comes from

The United States has the world's largest reactor fleet but mines very little of its own uranium. EIA's 2025 Uranium Marketing Annual Report gives the picture for purchases by U.S. reactor owners.

Origin of uranium delivered, 2025	Share
Canada	32%
Kazakhstan	28%
Australia	15%
Uzbekistan	7%
United States	7%
Others, including Russia	about 11% combined

Total purchases were 46.9 million pounds of U3O8 equivalent at a weighted average of $58.46 per pound. Enrichment is where Russia matters most. EIA reports 77 percent of the SWU bought in 2025 was foreign-origin, and 26 percent of that foreign share came from Russia. Multiply: 0.77 × 0.26 ≈ 0.20, so about one fifth of all enrichment purchased in 2025 came from Russia. (That 20 percent is a calculation from EIA's figures, not a number EIA states directly.)

The Russian uranium ban

The Prohibiting Russian Uranium Imports Act became Public Law 118-62 on May 13, 2024. Ninety days later, imports of unirradiated low-enriched uranium produced in Russia were banned. The law lets the Secretary of Energy grant waivers if no other supply is available to keep a reactor running or if imports are in the national interest, but only up to annual caps: 476,536 kg for 2024, falling to 459,083 kg for 2027. Every waiver ends no later than January 1, 2028. The ban runs through 2040.

In November 2024 the Russian government announced a temporary ban on enriched uranium exports to the United States, with case-by-case exceptions, which shortened the practical runway further. Separately, Section 102 of the ADVANCE Act (Public Law 118-67) bars the NRC from licensing possession of fuel assemblies made by companies owned or controlled by the Russian or Chinese governments unless the Energy and State secretaries jointly find that it poses no threat to national security.

The HALEU bottleneck

For advanced reactors the squeeze is sharper. DOE states plainly that HALEU "is not currently available from domestic suppliers" at commercial scale, and for years the only commercial seller was Russia's Tenex. TerraPower said in December 2022 that the loss of Russian HALEU would push Natrium's startup back by at least two years.

The domestic response so far:

• Centrus Energy, Piketon, Ohio: a small NRC-licensed centrifuge cascade producing HALEU under contract with DOE, the first licensed HALEU production in the country. Output has been in the hundreds of kilograms per year, against industry estimates of many tonnes needed per year by the 2030s.
• DOE's HALEU Availability Program: created by the Energy Act of 2020, it buys HALEU from domestic suppliers and allocates it to reactor developers. DOE's page lists an allocation process step dated July 2026.
• Recovered material at INL: DOE has been processing used EBR-II fuel at Idaho National Laboratory into HALEU feedstock; Oklo's first Aurora core is meant to use some of it.
• Executive Order 14302 (May 2025): directed DOE to plan expanded conversion and enrichment for LEU, HALEU and HEU, and to use Defense Production Act agreements to buy fuel cooperatively.

Treat any advanced reactor schedule as dependent on a fuel contract. If a developer cannot name its HALEU source and quantity, the start date is a hope.