Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesThey are less favourable to the search for compactness, however, than the stackable containers. Thesection in the access drifts to the cells may have to be increased to deal with the container size, whichmay also present a handicap for transfer through a shaft.The "stackability" of mid-size packages optimises the geometric shape of the "cell-package"combination, resulting in greater repository compactness. They are more suitable for transfert througha shaft and allow to optimise the access drift cross section.4.1.2.3 Solution adoptedThe solution adopted is a concrete, parallelepipedal container. It weighs less than about 25 tonnes. Itcan group up to four primary waste packages per waste disposal package [41].The external geometry of the container is standardised according to a limited number of models. Itswidth and height are limited to 2.5 metres. Its length (dimension sideways to cell) may exceed2.5 metres, but no more than 3 metres, for some primary packages. It is stackable over several levels inthe disposal cell.The parallelepipedal shape allows to minimise the external residual voids and at the same timefacilities possible retrieval with the simple, robust handling methods used for the emplacement. Thesolid concrete design inside the disposal package ensures that the residual voids around the primarypackages are virtually negligible.Concrete also provides mechanical integrity for a period of at least one hundred years with respect topossible package retrieval.For primary packages releasing hydrogen through radiolysis, the risk of excessive accumulation in thecontainer can be avoided by creating vents in the over-packing. Note also that as long as the concreteis in a dry atmosphere, the porosity alone of the concrete will evacuate the hydrogen sufficiently.Lastly, the disposal package is not designed to guarantee radiological protection with respect toexternal exposure to radiation.• Grouping of primary waste packages and standardisation of disposal containersWaste disposal package standardisation meets the need for simplicity and reliability in operation andthe limiting of the flow of parcels to be handled, while respecting package grouping possibilities in thecells based on their physico-chemical and radioactive characteristics. Thus all the diverse B waste inthe inventory presented in Chapter 3 may be disposed of based on seven dimensional classes of wastedisposal package.Most disposal packages (over 80%) have standardised lengths and heights of between 1.5 and2.1 metres. These disposal packages all contain four primary packages.The other disposal packages (under 20%) are larger. They are between 2.5 and 2.9 metres long and1.7 and 2.4 metres high. These disposal packages contain four primary packages, or only one or two inthe event the primary waste package are very large.• Make-up of a standard disposal containerA disposal container (Figure 4.1.2) is made up of two, pre-fabricated concrete components: a body anda lid.The body has internal partitions forming the compartments adjusted to the primary package shape. Theclearance between the internal diameter of each compartment and the external diameter of the primarypackage is sufficiently large (functional clearance) to emplace the primary packages and sufficientlysmall (small residual void) not to require filling once the primary package is in place. This approachfavours the possible recovery of the primary packages and avoids filling operations in an irradiatingenvironment.Once the primary packages are in place, the detachable lid fits into the container body.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM112/495