ASN Report 2017

378 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 13  - Nuclear fuel cycle installations T he nuclear fuel cycle begins with the extraction of uranium ore and ends with packaging of the various radioactive wastes from the spent fuels so that they can be sent for disposal. In France, all the uranium mines have been closed since 2000, so the fuel cycle concerns the steps involved in the fabrication of the fuel and then its reprocessing once it has been used in nuclear reactors. The licensees of the nuclear fuel cycle plants are part either of the Areva group, or of EDF (Framatome formerly Areva NP) * : Areva NC operates Mélox in Marcoule, the plants at La Hague, certain plants in Tricastin (Comurhex, TU5, W, Atlas, uranium storage areas in Tricastin, P35), as well as Malvési (which is an Installation Classified for Protection of the Environment – ICPE), the Tricastin enrichment company operates the Georges Besse II plant (GB II), Framatome operates Romans-sur-Isère (former FBFC and former Cerca). 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 an impact on safety. ASN therefore periodically asks that together with the fuel cycle companies EDF provide elements to demonstrate long-term compatibility between changes in fuel characteristics and fuel management and developments in fuel cycle installations and the corresponding transports. EDF transmits a “Cycle impact” file in response to this request. 1. The fuel cycle 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 by the Comurhex facilities in Malvési and Tricastin belonging to Areva NC. The facilities in question – most of 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 NPPs use uranium which is slightly enriched in uranium-235. For example, the fleet of Pressurised Water Reactors (PWR) requires uranium enriched to between 3% and 6% with the U-235 isotope. In France, uranium hexafluoride (UF 6 ) enrichment is carried out using an ultra- centrifuge process in the GB II plant at 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 placed in the reactor core where they release energy, notably through the fission of uranium-235 nuclei. After a period of use of about three to four years, the spent fuel is removed from the reactor and cooled in a pool, firstly on the site of the plant in which it was used and then in the Areva NC reprocessing 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 new fuels. The radioactive waste produced by these operations is disposed of in a surface repository if it is low-level waste, otherwise it is placed in storage pending a final disposal solution 2 . The plutonium resulting from the reprocessing of uranium oxide fuels is used in the Areva NC plant in Marcoule, called “Mélox”, to fabricate MOX fuel (mixture of uranium and plutonium oxides) which is used in certain 900 MWe nuclear power reactors in France. The MOX nuclear fuels are not reprocessed after being used in the reactors. They would only be reprocessed if future fast neutron reactors were to be commissioned. Since the shutdown of the Superphénix reactor in 1996, no company has as yet initiated the official process to build such a reactor (see chapter 12). CEA is studying a fast neutron reactor prototype called Astrid (see chapter 14). 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. 1 . Transuranic elements are chemical elements heavier than uranium. 2 . Storage is temporary, while disposal is final. * See point 3.3 of this chapter covering the reorganisation