Tome Architecture and management of a geological repository - Andra

5 – B waste repository zonein the order of around ten watts. It will be about three watts by 2025. The equivalent β-γ dose rate inpseudo-contact with the packages (5 cm) is currently in the order of 4 Sv/h; it will be in the order of0.5 Sv/h by 2025. Water radiolysis in the cementing matrix produces hydrogen.• Compacted cladding waste (reference packages B5)As indicated previously, a new method of conditioning cladding waste was introduced on the LaHague site in 2002. This involves compacting waste placed preliminarily in claddings, before beingmoved to stainless steel containers (CSD-C). The compacting process is applied to cladding wasteproduced from NUGG and PWR fuels reprocessed previously and now stored in silos and pits, andcladding waste produced from current and future reprocessing operations of fuel unloaded from thePRW reactors. As mentioned above, some packages also contain compacted technological waste fromthe site's operating and/or maintenance shops. Given the diversity and nature of the waste throughputsin question, distinction is made between four sub-assemblies of compacted cladding waste packages(CSD-C).The first package sub-assembly contains cladding waste from UOX, enriched recycled uranium andMOX fuel reprocessing mixed with metallic and organic technological waste. The hypotheses adoptedare (i) fuel reprocessing on average eight years after unloading from reactors and (ii) average weightof 420 kilograms of conditioned waste per package (including compacting claddings). Based on thesehypotheses, the heat rating of the packages, calculated for an envelope radiological inventory of thevarious waste flows mentioned above, is around 30 watts. Thermal decay of these packages is givenin Figure 5.1.12.Package irradiation level, initially around fifty sieverts per hour (Sv/h) is in the order of 15 Sv/h after aten-year cooling period. The radiolysis of the organic waste in the packages made up of technologicalwaste produces hydrogen. Note also that radioactive elements such as tritium (with the symbol T or3 H), carbon-14 ( 14 C), chlorine-36 ( 36 Cl), argon-39 ( 39 Ar) and krypton-85 ( 85 Kr) can be released in agaseous form. The finished package weighs approximately 520 kilograms.Like the previous packages, the second package sub-assembly contains a mixture of UOX, enrichedrecycled uranium and MOX cladding waste and technological waste. It differs from the first in thetype of technological waste, here formed of metallic materials only. Unlike the first sub-assemblypackages, it does not therefore generate hydrogen through radiolysis. However, there is a risk of thewaste releasing traces of radioactive gases ( 3 H, 14 C, 36 Cl, 39 Ar and 85 Kr). This raises the question oftheir containment as close to the waste as possible; this issue is dealt with in section 5.3. The otherpackage characteristics (heat rating, equivalent dose rate, weight) are otherwise identical to the firstsub-assembly.The third package sub-assembly only contains cladding waste from PWR fuels reprocessed in the pastand now stored. The packages weigh 725 kilograms on average. Given the age of the waste, thepackages do not transfer heat. Their irradiation level is around 5 Sv/h; it will be around 1 Sv/h by2025.The third package sub-assembly only contains cladding waste from NUGG fuels reprocessed in thepast and now stored. The finished packages weigh 350 kilograms on average. Given the age of thewaste, the packages do not transfer heat. Their irradiation level is also lower than for the previous subassemblies,namely around 0.4 Sv/h.Table 5.1.3 summarises the principal characteristics of the four sub-assemblies of compacted claddingwaste packages.Dossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY108/228