Tome Architecture and management of a geological repository - Andra
Tome Architecture and management of a geological repository - Andra
Tome Architecture and management of a geological repository - Andra
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2 – High-Level <strong>and</strong> Long-Lived wastemore numerous <strong>and</strong> more diverse through their conditioning. B waste primary packages are describedin chapter 5.2.2.3 Spent fuelIn terms <strong>of</strong> mass <strong>and</strong> quantity, spent fuel as studied in the exploratory direct disposal hypothesisessentially originates from fuel removed from EDF PWR reactors fleet. The radiological inventory <strong>of</strong>this spent fuel generates significant heat release as it does for C waste. However this heat release takeslonger to decay because <strong>of</strong> the contribution <strong>of</strong> plutonium <strong>and</strong> isotopes produced by decay (daughterproducts). Other specific characteristics <strong>of</strong> this spent fuel are the large dimensions <strong>of</strong> the assemblies<strong>and</strong> their fissile material content in relation to the issue <strong>of</strong> criticality risk.As previously indicated, fuels from former cycle back-ends (NUGG, EL4), research reactors <strong>and</strong>National Defence activities are to be added to the spent fuel from the PWR reactors. A description <strong>of</strong>these spent fuels is available in chapter 7.2.3 The inventory modelThe review <strong>of</strong> waste <strong>and</strong> the definition <strong>of</strong> their conditioning mode lead to a very wide variety <strong>of</strong> HLLLwaste primary package families (total <strong>of</strong> 61). They differ in chemical <strong>and</strong> radiological content, theirthermal <strong>and</strong> radiation output according to the presence <strong>of</strong> certain radionuclides, their nature, packaginggeometry <strong>and</strong> quantity.All the preceding data <strong>and</strong> hypotheses on the primary waste packages have been collated in an"inventory model" [3].This inventory model, on the basis <strong>of</strong> which both the clay <strong>and</strong> granite medium <strong>repository</strong> studies aregrounded, is organised using a tree-diagram structure. The tree-diagram structure groups primarypackages showing similar issues in terms <strong>of</strong> waste <strong>management</strong>.To cover the characteristics <strong>of</strong> the primary packages thus grouped, the inventory model defines "wastereference packages" (package types) which are representative <strong>of</strong> these groups.The tree-diagram nomenclature adopted to identify the waste reference packages will be usedthroughout the following chapters. It has three levels. Level 1 differentiates in traditional fashionbetween the various categories (B waste, C waste <strong>and</strong> spent fuel identified by the letters "CU").Various types <strong>of</strong> packages are identified within each <strong>of</strong> these categories, particularly for category Bwaste, based on waste type (sludge, technological waste, cladding waste from fuel assemblies, etc.)<strong>and</strong> conditioning methods (compacting, bituminisation, cementation). Breaking down level 1 <strong>of</strong> theinventory model into one or even two additional sub-levels, when necessary, provides a more detaileddescription on the variability <strong>of</strong> primary waste packages for design study, modelling <strong>and</strong> <strong>repository</strong>safety evaluation purposes. The following criteria are taken into account to differentiate between level2 or level 3 waste reference packages: physico-chemical characteristics <strong>of</strong> the conditioned waste (inconnection with the waste material <strong>and</strong> conditioning matrices), heat rating <strong>and</strong> irradiation levels <strong>of</strong> thepackages (in connection with the radiological inventory) <strong>and</strong> container characteristics (dimensions,materials). Thus, for waste package types encompassing a wide range <strong>of</strong> primary package families,such as the B3 waste reference package, a second level in the tree-diagram is created to grouppackages initially based on the type <strong>of</strong> package materials (concrete, steel) <strong>and</strong> whether or not theconditioned waste is homogenous.The physico-chemical characteristics <strong>of</strong> the conditioned waste have tremendous influence on thedesign choices, so that the packages are placed in favourable environmental conditions to limit theiralteration over time. They determine the initial <strong>and</strong> long-term containment capability <strong>of</strong> the packages<strong>and</strong> disturbances potentially caused by their degradation. These disturbances include (i) the release <strong>of</strong>products likely to increase radionuclides solubility or to complex a significant number <strong>of</strong>radionuclides, (ii) gas production by radiolysis or corrosion <strong>of</strong> materials <strong>and</strong> (iii) the formation <strong>of</strong>potentially aggressive species for the surrounding materials. In particular, packages containing organicDossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY23/228
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