Architecture and management of a geological repository - Andra

9 – Nuclear operating resources in the repositoryHowever, differences in the geometry of the three types of disposal package (B, C and CU) have led tothe adoption of specific transfer casks for each type. The diagrams in Figure 9.2.2 illustrate these threetypes of transfer cask.The use of protective casks is common in the nuclear industry. For example, Figure 9.2.3 illustrates asimilar transfer cask envisaged for the disposal of highly radioactive transuranium "RH" (Remotehandled) type wastes in WIPP installations (Waste Isolation Pilot Plant – USA).Figure 9.2.2 Transfer transfer casks for B, C and spentfuel packagesFigure 9.2.3 Transfer transfercask for disposal packages(photo from WIPP)9.2.2.2 Description of the three types of transfer cask• The transfer cask for B wastesThe radiological protection transfer cask for the disposal package of B wastes, consists of a base, ashielded parallelepiped-shaped container and a two-flap door system. It has no on-board mechanicalcomponents because the loading and unloading operations are conducted by separate equipment. Thewalls of the transfer casks are made of materials suited to the types of radiation emitted by the wastepackages transported (lead or steel for γ radiation, neutron-absorbing material for neutrons), and ifnecessary a heat shield for protection against fire risks.The existence of several types of disposal package for B wastes, in terms of dimensions, weight anddose equivalent rates has led to the definition of several categories of transfer casks. Their full weightsvary from 40 to 100 tonnes for packages of 7 to 25 tonnes. Their radiological protection thicknessesvary from 50 to 300 mm of steel or composite material depending on the equivalent dose rate of thepackages transported.• The transfer casks for C wastes and spent fuelsIn the case of C wastes and spent fuels, the shielded container is cylindrical and the door is a "sliding"type. In both cases, the transfer cask is fitted with an on-board mechanical unit consisting of a robotsituated inside the shielded container. This is a hydraulic jack-actuated push robot in the case of Cwastes and an air-cushion transporter robot in the case of the spent fuels. These robots are used toextract the packages and place them in the cell.The shielded container has walls made of steel/PPB/steel sandwich panels. The PPB(Plaster/Polyethylene with Boron addition), a neutron-absorbing material, has been chosen because ofthe type of radiation emitted by vitrified C wastes and spent fuels. The total thickness of the side walls,bottom and the door is of the order of 400 mm for the C transfer cask and of the order of 200 mm forthe spent fuel transfer cask.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM338/495