1 The “fuel cycle” 1. Transuranic elements are chemical elements heavier than uranium (atomic number 92). The main ones are neptunium (93), plutonium (94), americium (95), curium (96). In a reactor, they are derived from uranium during secondary reactions other than fission. The uranium ore is extracted, then purified and concentrated into Yellow Cake on the mining sites. The solid concentrate is then transformed into uranium hexafluoride (UF6) through a series of conversion operations. These operations are performed in the Orano plants in Malvési and Tricastin. These plants, which are regulated under the legislation for Installations Classified for Protection of the Environment (ICPEs) use natural uranium in which the uranium-235 content is around 0.7%. Most of the world’s nuclear power reactors use uranium slightly enriched with uranium-235. The Pressurised Water Reactor (PWR) series for example requires uranium enriched with isotope-235. In France, UF6 enrichment between 3 % and 6 % is carried out by ultracentrifuges in the Georges Besse II (GB II) plant in Tricastin. This enriched UF6 is then transformed into uranium oxide powder in the Framatome plant in Romans-sur-Isère. The fuel pellets manufactured with this oxide are introduced into cladding to make fuel rods, which are then combined to form fuel assemblies. These assemblies are then inserted into the reactor core, where they deliver energy, notably by fission of uranium-235 nuclei. Before it is used in the reactors, fresh nuclear fuel can be stored in one of the two Inter-Regional fuel Stores (MIR) operated by EDF in Bugey and Chinon. In 2023, Framatome also took over the fabrication of fuel assemblies based on Enriched Reprocessed Uranium (URE) intended for the Cruas-Meysse Nuclear Power Plant (NPP). After a period of use of about 3 to 4 years, the spent fuel assemblies are removed from the reactor and cooled in a pool, firstly on the site of the plant in which they were used and then in the Orano reprocessing plant at La Hague. In this plant, the uranium and plutonium from the spent fuels are then separated from the fission products and other transuranic elements(1). The uranium and plutonium are packaged and then stored for subsequent re-use. The “nuclear fuel cycle” begins with the extraction of uranium ore and ends with the packaging of the various radioactive wastes from spent fuel for subsequent disposal. In France, the last uranium mines closed in the year 2000, so the “fuel cycle” concerns the fabrication of fuel, its reprocessing after use in the nuclear reactors, the reuse of any products resulting from reprocessing that can be recycled, and waste management. The nuclear facilities involved in the “fuel cycle”, each of which is unique, are the links in a chain, the operation of which can be significantly disrupted if one of the links is defective. The licensees of the “fuel cycle” plants are part of the Orano or EDF (Framatome) groups: Orano Cycle operates the Melox plant in Marcoule, the La Hague plants, all the Tricastin plants, as well as the Malvési facilities. Framatome operates the facilities on the Romans-sur-Isère site. The French Nuclear Safety Authority (ASN) monitors the safety of these industrial facilities, which handle radioactive substances such as uranium or plutonium and constitute specific safety risks, notably radiological risks associated with toxic risks. ASN monitors the overall consistency of the industrial choices made with regard to fuel management and which could have consequences for safety. In 2023, on the La Hague site, Orano commissioned three New fission products evaporator-concentrators (NCPF T2) in the UP3-A plant, thus replacing the existing equipment which suffered from more advanced corrosion than foreseen in the design, plus a further expansion of the plutonium-bearing materials storage capacity. The situation of the Melox plant improved in 2023 by comparison with the previous years, in terms of quality and quantity of MOX fuel production (Mixture of OXides of uranium and plutonium). These factors are helping to stabilise the operation of the “fuel cycle”, even if this still offers little margin for contingencies and the countermeasures to be put into place to offset the risk of saturation of the spent fuel storage pool are yet to be deployed. With regard to the performance of the sites in 2023 and the measures taken by their licensees to improve them, ASN considers that the operation of the “fuel cycle” as a whole is improving, but remains fragile. 12 330 ASN Report on the state of nuclear safety and radiation protection in France in 2023 • 12 • “Nuclear fuel cycle” facilities
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