02 03 04 05 06 07 08 09 10 11 12 13 01 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 Treatment Station (STE2) and the Spent fuel reprocessing unit (AT1 – BNI 38), the radio- active sources fabrication unit (ELAN IIB – BNI 47) and the “Oxide High Activity” (HAO) unit, created for reprocessing fuels 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. 2.5 The support facilities (storage and treatment of radioactive effluent and waste) Many of these facilities, most of which were commissioned in the 1960’s and whose level of safety does not comply with current best practices, have been shut down. Old storage facilities were not initially designed to allow the removal of the waste, and in some cases they were seen as being the definitive waste disposal site. Examples include the silos at Saint-Laurent-des-Eaux (BNI 74), the pits, trenches and hangars of BNI 56, and the shafts of BNIs 72 and 166. Retrieval of the waste from these facilities is complex and will span several decades. The waste must then be packaged and stored again in safe conditions. New packaging and storage facilities are thus either planned or actually under construction. The STEs for their part have been shut down due to their ageing or because the facilities producing the effluents treated in these stations have stopped functioning. Examples include BNI 37-B at Cadarache and STE2 at the La Hague plant (BNI 38). The difficulties associated with decommissioning of the STEs are closely linked to their shutdown conditions, particularly the emptying and rinsing of their tanks. The decommissioning of these support facilities raises many issues. Firstly, poor knowledge of the operating history and the state of the facility to be decommissioned (taking account of the corrosion of waste drums or pollution of soils resulting from significant events that occurred when in service, for example) necessitates prior characterisation of the stored legacy waste and of the sludges or deposits present in certain tanks and silos. Moreover, taking into account the quantities, the physical and chemical forms and the radiotoxicity of the waste contained in these facilities, the licensee must develop means and skills that involve complex engineering techniques (radiation protection, chemistry, mechanics, electrochemistry, robotics, artificial intelligence, etc.). In fact, this waste is highly irradiating and heterogeneous, as it comprises structural elements from fuel reprocessing, technological waste, rubble, soils and sludge. Some of the waste has been stored in bulk with no prior sorting. The retrieval operations therefore require remotely operated pick-up means, conveyor systems, sorting systems, sludge pumping and waste packaging systems. The development of these means, carrying out the operations under conditions ensuring a satisfactory level of safety and radiation protection, and perhaps even the creation of new waste retrieval and packaging facilities represent a major challenge for the licensee. Given that these operations can last several decades, the management of ageing of the facilities is also a challenge. ASN Report on the state of nuclear safety and radiation protection in France in 2024 359 Decommissioning of Basic Nuclear Installations 14 15 AP
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