LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT challenges comes from the production and management of large volumes of very low-level waste, which must be stored then disposed of via an appropriate route. There is a considerable amount of decommissioning experience feedback for the research reactors, given the decommissioning of numerous similar installations in France (Siloé, Siloette, Mélusine, Harmonie, Triton(3), the Strasbourg University Reactor – RUS) and abroad. Their decommissioning usually spans about ten years, but the large number of installations to be decommissioned simultaneously may lead to significantly longer prospective decommissioning durations for some of CEA’s reactors. After clean-out of the activated or contaminated areas and subsequent removal of all the radioactive waste to appropriate disposal routes, the majority of these reactors were demolished and the waste sent to conventional waste disposal routes. 2.3 The front-end “nuclear fuel cycle” facilities Two front-end “nuclear fuel cycle” facilities are undergoing decommissioning. They are located on the Tricastin site, one specialising in uranium enrichment by gaseous diffusion (GeorgeBesse I plant – BNI 93), the other in uranium conversion (former Comurhex plant – BNI 105). The only radioactive materials used in these plants were uraniumbearing substances. One of the particularities of these facilities therefore lies in the presence of radioactive contamination associated with the presence of “alpha” particle-emitting uranium isotopes. The radiation protection issues are therefore to a large extent linked to the risk of internal contamination. Furthermore, these are older facilities whose operating history is poorly known. Determining the initial state, particularly the pollution present in the soils beneath the structures, therefore remains an important issue. Moreover, the industrial processes implemented back then involved the use of large quantities of toxic chemical substances (such as chlorine trifluoride and hydrogen fluoride, in addition to the uranium itself): the containment of these chemical substances therefore also represents a risk on these facilities and can necessitate the deployment of dedicated means (ventilation, containment air locks, respiratory protection masks, etc.). Materials and wastes are currently being retrieved at the Comurhex facility (BNI 105), with the aim of removing them from legacy storage areas for reprocessing and final conditioning. Against this backdrop, ASNR has given Orano Chimie-Enrichissement formal notice to finalise the removal from storage of the materials present in area 61 by September 2026, in view of the safety issues associated with the storage of these unburnt fluorination residues. 2.4 The back-end “nuclear fuel cycle” facilities The back-end facilities of the “nuclear fuel cycle” are the spent fuel storage pools, the spent fuel reprocessing plants and the facilities for storing waste from the treatment process. These facilities operated by Orano are situated on the La Hague site. The first processing facility at La Hague was commissioned in 1966, initially for reprocessing the fuel from the first-generation GCRs. This facility, BNI 33, called “UP2-400” standing for “Production Unit No. 2 – 400 tonnes”, was definitively shut down on 1 January 2004 along with its support facilities: the Effluent and Solid Waste Treatment Station (STE2) and the Spent fuel reprocessing unit (AT1 – BNI 38), the radioactive sources fabrication unit (ELAN IIB – BNI 47) and the “Oxide High Activity” (HAO) unit, created for reprocessing fuels 3. Triton was one of the first highly compact and flexible pool-type research reactors called “MTR” (Material Test Reactor). Triton (6.5 MWth) was installed on the Fontenay-aux-Roses site in 1959. from the “light water” reactors (BNI 80). Some of these facilities experienced accidents which contaminated the premises and their near environment, such as the fire in silo 130 belonging to BNI 38, in 1981. Unlike the direct on-line packaging of the waste generated by the UP2-800 and UP3-A plants in operation, most of the waste generated by the first reprocessing plant was stored without treatment or packaging. Decommissioning is therefore carried out concomitantly with the legacy Waste Retrieval and Packaging (WRP) operations. About ten projects of this type are currently in progress in the old facilities (silos STE2, 115 and 130 in BNI 38 and the HAO silo in BNI 80). They will span several decades and are a prerequisite to the complete decommissioning of these facilities, whereas the decommissioning of the process parts of the plant is continuing with more conventional techniques. At the La Hague site, facilities undergoing decommissioning interact with facilities in operation (see chapter 10 on the “fuel cycle”). In particular, effluent transfers at the La Hague site are carried out using transfer lines (pipes) located in buried or flush concrete structures called channels. Orano was required to reroute all the first-generation channels at the La Hague site by the end of 2024. The vast majority of these first-generation channels are not equipped with leakage recovery systems, and their obsolescence means that they cannot guarantee their safety function of containing the liquid radioactive effluents they carry in the long term. These channels are used in particular to transfer effluent between operating facilities at the La Hague site (BNIs 117 and 118). The licensee informed ASN in 2024 that it would not be able to comply with this requirement, and requested an extension of the use of certain channels until the end of 2025 and the end of 2028, in view of the unexpected issues encountered and the complexity of the work involved in rerouting the effluent transfer lines between the different plants on the site. Considering that Orano must end the use of first-generation channels on the La Hague site, ASNR has given Orano formal notice to reroute the various remaining lines with first-generation channels, according to a schedule running from the end of 2025 to the end of 2028. The licensee must also present and implement compensatory measures to prevent the identified risk of soil contamination in the event of a leak, pending the actual rerouting of the channels concerned. HIGHLIGHT No.2 Destruction of the cooling towers at the Georges Besse uranium enrichment plant (BNI 93) Erected in the early 1970s, the two towers, 123 metres high and 90 metres in diameter at their base, were used to cool the Georges Besse uranium enrichment plant for 33 years. Following the shutdown of the facility in 2012, decommissioning of the plant began in 2020 and dismantling of the towers began in April 2025. This operation is expected to last 18 months. The method used to demolish the two towers is “nibbling”. It consists of dismantling the concrete shell of the towers, piece by piece, from top to bottom, using a hydraulic shear installed on a crane positioned at the centre of the tower. This method limits some of the direct impacts of the worksite, such as vibrations and dust. The 25,000 tonnes of non-radioactive materials that will be recovered are destined for subsequent recycling. ASN approved the dismantling of the towers in July 2024, and the dismantling of the first tower was completed in August 2025. 342 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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