Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesThis chapter has a dual purpose. Firstly, it describes the reasons behind B and C waste over-packingand the functions of a spent fuel disposal container. Secondly, it describes their design principles andtheir justifies that manufacture, handling and performances are realistic.The primary design motivations for a waste disposal package are linked to their reliability and to thestandardisation of handling equipment in underground facilities. They also relate to the potentialcontribution of a waste disposal package to reversible repository management. Lastly, the disposalpackages contribute to the long-term safety functions, particularly in protecting waste from processessusceptible to cause their alteration and by controlling radionuclide release.This chapter describes the packing solutions studied for all waste categories. It shows that a concreteover-pack, regrouping several primary waste packages, is a suitable solution for B waste. It also showswhy a metallic container seems more relevant for C waste and spent fuels. Include steel offersexcellent resistance to temperature and total, reliable watertightness over long periods.This chapter also presents the results of the real-scale waste disposal package demonstratorprogramme for B waste and spent fuels.4.1 B disposal waste packagesB primary waste packages vary tremendously in size, shape, characteristics and handling methods.Compactness, ease of handling and reversible repository management are all objectives that gave riseto the question of over-packing for B waste, thus simplifying the operating processes in undergroundfacilities.These considerations were shared with the Atomic Energy Commission (CEA), itself dealing with asimilar problem in their long-term storage study. As result, a joint container solution was reached forlong-term storage and for disposal. Note that this opens up the possibility of receiving on a repositorysite waste already contained in "storage and disposal" packages, as described below, rather than as theprimary waste packages described in Chapter 3.4.1.1 Discussion of principal issues4.1.1.1 Interest of over-packing for B wasteChapter 2 introduced the search for compactness in the repository architecture (§ 2.4.1.4). Thisresearch resulted in a disposal cell design with waste packages occupying the excavated area in thebest way possible, by being placed close together. This has a strong influence on the packageemplacement process.The majority of B waste packages are irradiating (see § 3.2.1). To protect man against radiation fromwaste while allowing access to the B waste disposal cells, the disposal package must be either verythick to attenuate this radiation sufficiently (for example, one metre-thick concrete), or structuresproviding radiological protection must be built close to the waste disposal packages. Neither of theseoptions, however, make optimum use of the excavated volume.Andra thus adopted irradiating cells: as soon as a first waste package is introduced, operator presencein the majority of cells is banned. Operations taking place in these cells are therefore controlledautomatically or remotely.The choice of irradiating cells reinforces the interest in making underground operations as simple aspossible: this involves encouraging the automation of repetitive actions, particularly packageemplacement, and performing these operations with excellent operating safety. Faced with a technicalproblem, human intervention will be made difficult, if not impossible, by the radiation; theintervention will therefore be performed via remote control.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM106/495