ASN Report 2020

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 (UF 6 ) 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, UF 6 enrichment between 3% and 6% is carried out by ultracentrifuges in the Georges Besse II plant in Tricastin. This enriched UF 6 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. After a period of use of about three to four 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 recycling plant at La Hague. In this plant, the uranium and plutonium from the spent fuels are separated from the fission products and other transuranic elements (1) . The uranium and plutonium are packaged and then stored for subsequent re-use. However, at present, the uranium obtained from this reprocessing is no longer used to produce fresh fuels. EDF announced its intention to resume its use in 2023, after re-enrichment of the reprocessed uranium in Russia. The plutonium resulting from the reprocessing of uranium oxide fuels is used in the Orano plant in Marcoule, called “Melox”, to fabricate MOX fuel (mixture of uranium and plutonium oxides) which is used in certain 900 Megawatts electric (MWe) nuclear power reactors in France. The MOX nuclear fuels are not currently reprocessed after being used in the reactors. Pending reprocessing or disposal, the spent MOX fuels are stored at the La Hague plant. The main material flows for the fuel cycle are presented in Table 1. Other facilities are needed for the operation of the Basic Nuclear Installations (BNIs) mentioned above, more particularly the “Socatri” facility, which is responsible for the maintenance and decommissioning of nuclear equipment, as well as the treatment of nuclear and industrial effluents from the Orano platform in Tricastin. 1.1  Front-end fuel cycle Before fuels are fabricated for use in the reactors, the uranium ore must undergo a number of chemical transformations, from the preparation of the “yellow cake” through to conversion into UF 6 , the form in which it is enriched. These operations take place primarily on the Orano sites of Malvési, in the Aude département , and Tricastin in the Drôme and Vaucluse département s (also known as the Pierrelatte site). On the Tricastin site, Orano operates: ∙ the former Comurhex facility (BNI 105) for converting uranium tetrafluoride (UF 4 ) into UF 6 , which contains the Philippe Coste plant; ∙ the Georges Besse II UF 6 ultra-centrifuge enrichment plant (BNI 168); ∙ the TU5 facility (BNI 155) for conversion of uranyl nitrate UO 2 (NO 3 ) 2 produced by reprocessing spent fuel at La Hague into uranium sesquioxide (U 3 O 8 ); ∙ the W plant (ICPE within the perimeter of BNI 155) for converting depleted UF 6 into U 3 O 8 ; 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 uraniummines were closed in 2000, so the fuel cycle concerns the fabrication of the fuel and then its reprocessing once it has been used in the nuclear reactors. The licensees of the fuel cycle plants are part of the Orano or EDF (Framatome) groups: Orano operates Melox 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 this context, ASN periodically asks EDF to submit a “Cycle Impact” file prepared jointly with the fuel cycle stakeholders and presenting the consequences – for each step of the “nuclear fuel cycle” – of EDF’s strategy for using the different types of fuel in its reactors. “Nuclear fuel cycle” installations 11 322 ASN Report on the state of nuclear safety and radiation protection in France in 2020