The nuclear fuel cycle is the set of industrial processes that take uranium from the ground and ultimately make spent fuel safe for long-term disposal. Each step is a separate licensed activity; each step has its own safety, radiation protection, criticality and safeguards issues.
Front end
Steps in the front end (before fuel reaches the reactor):
- Mining and milling — uranium is extracted as ore (typically 0.05-20% U) and processed into yellowcake (U3O8). Major producers: Kazakhstan, Canada, Australia, Namibia, Niger. Hazards: radon, dust, naturally radioactive tailings.
- Conversion — yellowcake → uranium hexafluoride (UF6) gas, the input form for enrichment. Major facilities: Cameco (CA), Orano Malvési+Pierrelatte (FR), ConverDyn (US), Tenex (RU), CNNC (CN).
- Enrichment — increasing U-235 from natural 0.711% to typical reactor fuel 3-5% (low-enriched uranium, LEU). All current commercial capacity uses gas centrifuges (URENCO, Orano, Tenex, CNNC). Future small reactor designs may use HALEU (high-assay LEU, 5-19.75%) which requires new licensing categories.
- Fuel fabrication — UF6 → UO2 pellets → fuel rods → fuel assemblies. Major plants: Westinghouse Columbia (US), Springfields (UK), AREVA Romans-sur-Isère and FBFC Dessel (FR/BE), Mitsubishi Tokai-Mura (JP), TVEL (RU).
Reactor use
Fuel typically resides three to five years in core, with an average burn-up of 40-55 GWd/tU. PWR fuel is loaded as fresh and burned with periodic reshuffling; BWR uses a similar approach with different rod geometry. CANDU reactors use natural uranium and operate on continuous on-power refuelling, so no separate enrichment step is required.
Back end
Steps in the back end (after fuel leaves the reactor):
- Wet storage in spent-fuel pools at the reactor site (years).
- Transport in Type B(U)F packages under IAEA SSR-6 / national packaging and transport regulations.
- Dry storage in casks, either on the reactor site or at a centralised facility.
- Reprocessing (optional) — chemical separation of uranium and plutonium for re-use; produces vitrified high-level waste, intermediate-level waste, and recovered uranium plus plutonium for MOX fabrication. Major facilities: La Hague (FR, Orano), Rokkasho (JP, partially commissioned), historical Sellafield Thorp+Magnox (UK, both shut down), Mayak (RU).
- MOX fabrication — uranium-plutonium mixed-oxide fuel. Facilities: Melox (FR), historical Sellafield MOX Plant (UK).
- Disposal — see Spent Fuel & Deep Disposal.
Open vs closed cycle
In an open cycle spent fuel is treated directly as waste and disposed. This is the current practice in Sweden, Finland, Canada, the United States (in practice, despite the original closed-cycle plans), Spain, Switzerland and most countries operating reactors. In a closed cycle spent fuel is reprocessed and the recovered uranium and plutonium are recycled into new fuel. This is current French practice for civilian fuel.
The choice between open and closed has changed historically with weapons-proliferation concerns, fuel-availability projections, and reprocessing economics. Most countries that started with closed-cycle ambitions in the 1970s have moved toward open-cycle practice.
Regulator's role at each step
Although each step has its own technical safety profile, the regulator's functions are similar: licensing of the facility and its activities; review of safety case (criticality, fire, radiation, conventional safety); inspection and supervision of operation; oversight of dose to workers and public; safeguards under IAEA agreements; transport approvals. National regulators typically delegate or partner with other authorities for transport (DOT in US; ASN with the road/rail regulators in FR; etc.).
Safeguards
Each enrichment, fabrication and reprocessing facility is subject to IAEA safeguards under the Comprehensive Safeguards Agreement (INFCIRC/153) and, in most countries, an Additional Protocol (INFCIRC/540). Safeguards inspection focuses on material accountancy and on the detection of undeclared activities. EU member states have an additional layer of Euratom safeguards.