Reprocessed Fuel and Uranium Savings in France

Allan Attia
March 10, 2026

Submitted as coursework for PH241, Stanford University, Winter 2026

Nuclear Power in France

Fig. 1: Example of a spent-fuel pool used for nuclear waste management (San Onofre Nuclear Generating Station near San Clemente, California. Source: Wikimedia Commons)

Electricity production in metropolitan France reached 547.5 terawatt-hours in 2025, and nuclear generation was 373.0 terawatt-hours that same year, representing about 68.1% of national electricity production. This electricity inevitably produces nuclear waste because it is generated by fission, which splits heavy atoms and leaves behind fission products and other radioactive by-products in the fuel. After several years of use in a reactor, often on the order of four to five years, fuel assemblies are removed because their performance declines and because radioactive by-products have accumulated. At that point, the used fuel becomes a management challenge, but also, in France's approach, a potential resource.

France's strategy is based on the fact that most of what is inside used fuel is not ultimate waste. Indeed, used fuel is composed of roughly 95% uranium and about 1% plutonium, both of which can be reused after chemical treatment, while around 4% becomes final waste. The crucial point is that the waste categories that matter most for long-term disposal are not the largest by volume. The smaller fractions, those that are highly radioactive and long-lived, are the ones that drive the design requirements for deep, permanent isolation.

What makes France distinctive is that it has operated, for decades, an industrial closed fuel cycle: it reprocesses part of its used fuel and manufactures new fuel from recovered plutonium, which is then loaded into a portion of the reactor fleet. By doing so, France reduces its demand for natural uranium, which is almost entirely imported, turning fuel recycling into more than a technical choice: it also becomes a question of sovereignty.

Nuclear Recycling in France

Used fuel assemblies removed from nuclear power plants across France are transported to the La Hague site. They are first stored under water in cooling pools (Fig. 1), where they remain for several years. It allows the heat and the most short-lived radioactive species to decrease, which makes later handling and processing manageable. [1]

Reprocessing begins by dealing with the parts that will not be reused. The fuel assemblies contain physical hardware, metallic structures, cladding, end pieces, and other components, that have been exposed to intense radiation and must be treated as waste once the fuel is processed. After this initial mechanical stage, the core objective of reprocessing is chemical: separating uranium and plutonium from the fission products. [1]

Fission products are the fragments created when a heavy nucleus splits. They include many different isotopes formed directly by fission and others formed by subsequent radioactive decay. They are considered final waste because they are highly radioactive, they generate heat, and they are not reusable as fuel. In practice, they are conditioned into stable waste forms designed for long-term isolation. [1,2]

Uranium and plutonium are treated differently because they still contain usable energy. In a typical reactor, only a small fraction of the heavy atoms in the fuel actually undergo fission. Most of the uranium remains uranium, and part of the uranium has been converted into plutonium by neutron capture during operation. That recovered plutonium is fissile, meaning it can sustain a chain reaction in a reactor, and recovered uranium can also be reused under certain fuel-cycle pathways after appropriate processing. [1,2]

The recovered plutonium is then used to fabricate a mixed fuel, commonly called MOX, which combines uranium oxide with plutonium oxide. [2,3]

Electricity From Mixed-Oxide Fuel

Let E_nuclear be France's annual nuclear electricity production, expressed in terawatt-hours per year. As a worked example, the national electricity balance reports E_nuclear = 373.0 terawatt-hours in 2025. [4] We then need the fraction f of nuclear electricity generated using mixed-oxide fuel. Orano states that mixed-oxide fuel accounts for about 10% of the nuclear electricity produced in France. [2] With f ≈ 0.10, the annual electricity associated with mixed-oxide fuel is therefore

E_mixed ≈ f E_nuclear = 0.10 × 373.0 TWh y^-1 = 37.3 TWh y^-1

It is useful to place this number in the context of the entire electricity system. Total electricity production from all sources combined in 2025 is 547.5 terawatt-hours, so 37.3 terawatt-hours corresponds to about 6.8% of all electricity produced that year. [4]

Natural Uranium Saved

To estimate the natural uranium scale associated with 37.3 terawatt-hours, we can use the relationship between annual nuclear electricity production and annual natural-uranium consumption for the French reactor fleet. A technical note from the French nuclear safety authority reports that the EDF fleet consumes on the order of 8,400 tonnes of natural uranium per year. [1] Using E_nuclear = 373.0 TWh/yr, this implies an average requirement of

8400 tonnes y^-1

373.0 TWh y^-1

22.5 tonnes TWh^-1

of natural uranium. Under that approximation, producing 37.3 terawatt-hours with conventional uranium fuel would require about

37.3 TWh × 22.5 tonnes TWh^-1 = 840 tonnes

Conclusion

France's recycling policy delivers two clear effects. First, it substitutes mixed-oxide fuel for uranium-only fuel in a portion of the reactor fleet. Quantitatively, this corresponds to tens of terawatt-hours per year and to a reduction in natural uranium demand on the order of hundreds of tonnes per year, based on the safety authority estimate. [1,2] Second, it changes the form of the most hazardous waste. Reprocessing concentrates fission products and certain long-lived materials into conditioned waste forms associated with the deep disposal pathway, while the national inventory shows that high-level and long-lived wastes exist in relatively small volume but dominate long-term management requirements. [5]

Recycling does not eliminate the need for long-term isolation. Even after uranium and plutonium are recovered, fission products remain and must be isolated over long timescales. Moreover, France's current practice does not reprocess spent mixed-oxide fuel after it has been used, that fuel is stored pending future decisions. [6] France's current recycling practice directly reduces the need for natural uranium, quantified here. Other meanings of less waste generally require different system choices, such as extracting more energy per unit of fuel, or developing technologies aimed at repeated recycling, each with its own engineering and policy constraints. [5,6]

© Allan Attia. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.