Uranium enrichment
The process of increasing the share of fissile U-235 in uranium above its natural 0.711%, to make reactor fuel or, at very high levels, weapons material.
Natural uranium is 99.28% U-238 and 0.711% U-235. Light-water reactors need low-enriched uranium (LEU) at 3–5% U-235; newer fuels go up to 5–10% (LEU+). HALEU, high-assay LEU between 5% and 20%, is required by many advanced reactors and SMRs. Above 20% is highly enriched uranium (HEU); weapons-grade material is about 90%.
Uranium is converted to uranium hexafluoride (UF6) and enriched almost entirely in gas centrifuges, which use about 50 kWh per separative work unit (SWU), around 2% of the energy of the gaseous diffusion plants they replaced.
Producing 1 kg of 4.5% LEU with 0.25% tails needs about 8.9 kg natural uranium and 6.9 SWU. A 1 GWe PWR uses roughly 20–25 t of enriched fuel per year, requiring roughly 150,000 SWU and about 200 t of natural uranium.
Global capacity is about 60 million SWU per year, held by Rosatom (about 40%), Urenco, Orano and CNNC. The US ban on Russian enriched uranium imports (waivers expiring 2028) has spurred expansions at Urenco USA, Orano's Georges Besse II and a planned Orano plant in Tennessee.
Related terms
All terms →- Nuclear fission
The splitting of a heavy atomic nucleus such as uranium-235 or plutonium-239 into lighter nuclei after absorbing a neutron, releasing about 200 MeV of energy and further neutrons.
- Pressurised water reactor (PWR)
The most common nuclear reactor type, in which water under high pressure cools the core without boiling and transfers heat to a separate steam circuit.
- SMR (Small Modular Reactor)
A nuclear reactor of up to about 300 MWe per module, designed for factory fabrication and modular deployment to cut construction time and financing risk.
- Burnup
The thermal energy extracted from nuclear fuel per unit mass of initial heavy metal, usually expressed in gigawatt-days per tonne (GWd/tHM).
- Thorium fuel cycle
A nuclear fuel cycle that uses fertile thorium-232, which absorbs a neutron and decays to fissile uranium-233, as an alternative to uranium-plutonium fuel.