Architecture and management of a geological repository - Andra

Firstly, its dimensioning: the selected materials it is made up of (mass concrete) and its physical andchemical environment provide for the durability and stability of the structure which houses thepackages for a period of at least a few centuries.Moreover, the shape of the lining is designed tominimise residual clearances between the liningand the disposal packages to avoid filling workwhich would imprison the packages and renderthem integral with the structure. The repositorychamber, which has a square cross-section,provides residual spaces between the stacks ofpackages and the lining with a width of the orderof 10 cm along the whole length of the cell.These clearances, which are unfilled, remainunchanged for a period equal to that of thelining's lifetime. The packages remain free insidethe cell. These conditions are the same as thoseprevailing during the phase in which they areimplaced. (Figure 10.4.1).• Durability of disposal packagesThe choice of concrete for the composition ofdisposal packages will provide multi-centurymechanical durability, especially in a weaklyaggressive environment. Regarding thereinforced concrete solutions selected, thecorrosion phenomenon of the reinforcement rodsis prevented through the use of multi-century,Figure 10.4.1 Functional clearances – Crosssection of a B package disposal cellnon-porous compact concrete, an adequate thickness of concrete liner and the use of stainless steel forthe frames.Lastly, the strength of the disposal package also durably limits–over a period of several centuries–therisks of dispersal of radioactive elements within the cell.10.4.1.2 Retrieval conditions at the “After package emplacement” stageAll of the equipment in the radiation chamber (port door and rotating table) is left in place. Ventilationof the cell is maintained.When all the packages have been placed in the cell (Figure 10.4.2), a radiological protection wallconsisting of concrete blocks may be erected between the last stacks of packages and the internalshielding door at the head of the cell, whereby making cell maintenance easier.Packages may be withdrawn at any time, just like in a storage situation. However, a serviceabilityinspection of the cell head section shall be conducted prior to this operation.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM420/495