Who converts uranium to UF6

This is the least glamorous stage in the chain and one of the two tightest.

Enrichment works by exploiting the tiny mass difference between U-235 and U-238, and the only practical way to do that at scale is to spin the uranium as a gas in a centrifuge. Uranium metal boils at over 4,000 °C. Uranium hexafluoride sublimes at 56 °C. That single chemical convenience is why UF6 sits between mining and enrichment, and why fluorine chemistry is a prerequisite for a nuclear fuel cycle.

UF6 is also unpleasant to handle. It reacts violently with water, including atmospheric moisture, producing hydrofluoric acid. Conversion plants are chemical plants with the safety case of chemical plants, and they are expensive to build and unrewarding to own.

That last point explains the market. Conversion was a low-margin business for most of the 2010s, and in 2017 Honeywell simply idled Metropolis, the only conversion plant in the United States, because the price no longer covered the cost. For six years the US converted no uranium at all. It restarted in 2023 when prices recovered after the invasion of Ukraine.