Who enriches uranium

Natural uranium is 0.71% U-235, the isotope that fissions readily, and 99.3% U-238, which does not. Almost every commercial reactor needs that fraction raised to between 3% and 5%.

The two isotopes are chemically identical. The only thing separating them is a mass difference of about 1.3%, and every enrichment technology ever deployed is a way of exploiting that difference repeatedly. Gaseous diffusion, the original method, pushed UF6 through porous barriers thousands of times in series and consumed staggering amounts of electricity — the French Georges Besse I plant used roughly 3% of France's electricity and had three dedicated reactors built to power it.

The gas centrifuge replaced it and uses about 2% as much energy per unit of work. Urenco commercialised it under the 1970 Treaty of Almelo, and that single technical shift is why enrichment is cheap today and why the industry consolidated around so few operators: a centrifuge plant is capital-intensive, export-controlled, and only economic at scale.

Enrichment is measured in Separative Work Units, which quantify the effort of separation rather than a mass of product. A SWU is not a tonne of anything; it is a unit of work, and the amount needed depends on how much U-235 you are willing to leave behind in the discarded tails.

The strategic weight of this stage became obvious in 2022. Russia supplied roughly a fifth of US enrichment services, and the US banned Russian uranium imports in May 2024 with waivers running to 2027. Rebuilding Western capacity is now a stated policy objective in both the US and Europe, but centrifuge plants take the better part of a decade to build.