Conversion to uranium hexafluoride

Uranium-235 and uranium-238 are chemically identical: any enrichment method has to separate them by their mass difference, just three atomic mass units. That requires a uranium compound that is a gas at a manageable temperature, so it can be centrifuged or diffused molecule by molecule. Uranium hexafluoride, UF₆, sublimes at about 56 °C and is the only practical candidate: that is why, before enrichment, all yellowcake is first converted into UF₆.

The process runs U₃O₈ through several chemical reactions, reduction, hydrofluorination and final fluorination, to obtain solid UF₆ that is packed into 48-inch steel cylinders for transport. It is an industry concentrated in very few plants: Cameco in Port Hope, Canada (12,500 tonnes-of-uranium-per-year capacity, 10,600 produced in 2022); Orano in Malvési and Tricastin, France (15,000 t/yr capacity, 8,900 produced); CNNC in Lanzhou and Hengyang, China (15,000 t/yr, 10,500 produced); and Rosatom in Seversk, Russia (12,500 t/yr, 12,000 produced, running near full capacity). World capacity adds up to about 62,000 tonnes of uranium a year, but actual 2022 output was only 42,000.

The fifth plant is ConverDyn, owned by Honeywell, in Metropolis, Illinois: the only US converter, with 7,000 tonnes of annual capacity and zero tonnes produced in 2022. It is the most visible face of a structural problem: outside Russia and China, Western conversion depends almost entirely on Canada and France, and the US plant went years without running at full capacity for lack of long-term contracts, even as demand from Western utilities grew. With only five commercial plants on the whole planet, any extended outage at one of them strains the rest of the chain before uranium even reaches enrichment.

That concentration is why the 48-inch cylinders became such a visible bottleneck in the fuel cycle: having uranium and centrifuges is not enough if there is nowhere to convert the yellowcake into gas first. Canada and France are, in practice, the only reliable Western suppliers of that intermediate step, and any country that wants to secure its supply chain without depending on Russia or China ends up depending on those two instead.

Argentina has its own UF₆ conversion capacity, though on a very different scale from the five commercial plants: CNEA converts uranium concentrate into hexafluoride at the Pilcaniyeu Technological Complex, near Bariloche, to feed its own enrichment plant on the same site. The World Nuclear Association puts its capacity at 60 tonnes of uranium a year, against the 7,000-15,000 t/yr of the five commercial converters, and does not count it among them: it is a plant built to supply the country's own enrichment, not to sell UF₆ abroad. The uranium dioxide that fuels the heavy-water reactors, Atucha I, Atucha II and Embalse, is instead produced by Dioxitek in Córdoba without going through UF₆, because those reactors need no enrichment. Dioxitek is also building a second plant in Formosa, still unfinished; in April 2026 the US company NANO Nuclear Energy proposed investing more than USD 230 million to complete it together with Dioxitek and produce natural uranium hexafluoride there.