Given the absence of structured and operational waste management solutions in France in the first decades of the French nuclear programme, some of the waste from the nuclear installations was stored in facilities which do not meet the safety standards in force today (silos, trenches). At the time, the licensees did not precisely characterise this waste and did not systematically produce detailed inventories. As part of the projects to decommission their old facilities, the licensees (CEA, EDF, Orano) are today carrying out “Waste Retrieval and Conditioning (WRC*)” projects for this legacy waste. Owing to their complexity, these projects generally take place over long periods of time. The licensees do not always have records or reliable knowledge of the waste stored in these facilities and have to carry out studies to physically and chemically characterise it, and identify the process(es) for retrieving it, along with the management solution associated with each type of waste (either already in existence or planned). For example, on the Orano La Hague site, silo 130 was designed for dry storage of solid waste produced by cladding removal from gas cooled reactor (GCR) irradiated fuels. It was operated from 1973 to 1981. It now contains solid waste, water, sludges and rubble. WRC operations started in 2019 and should be completed in 2056. Reprocessed uranium is obtained from spent fuels – based on enriched natural uranium – used in the pressurised water reactors and which have been reprocessed* in the Orano plant in La Hague since the 1980s. Reprocessed uranium was used to fabricate new fuel assemblies until 2013, and has been used in certain 900 MWe reactors. EDF resumed this utilisation in 2024, at Cruas-Meysse, and plans to expand it. The reuse of reprocessed uranium in the past, and the prospects for future reuse, explain why this radioactive substance is classified as a material rather than a waste. Reprocessed uranium is chemically transformed into uranium hexafluoride (UF6) in a plant in Seversk, Russia, the only facility in the world currently capable of performing this operation. Why is the reprocessed uranium stored at Tricastin considered to be a radioactive material rather than waste? After the repository is closed, most of the radioactive elements will remain trapped in the repository and the Callovo‑Oxfordian layer. Only a few soluble radioactive elements, not trapped by the clay and long‑lived (such as iodine-129, chlorine-36 and selenium-79) will migrate in the Callovo‑Oxfordian layer by diffusion, slowly and in a limited manner. Andra’s long-term scenarios conclude that there is no health or environmental impact. This will take at least several hundred thousand years. What will happen once Cigéo is full? What happens to legacy waste? Radioactive waste • 33
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