Architecture and management of a geological repository - Andra

5 – Repository ModulesThere are several possible solutions to the problem of positioning the container for insertion in thecell. The various figures shown illustrate the solution using pivoting. The operation is carried out in a“positioning chamber”, broadening the access drift at the cell location. The dimensions of thepackages require chambers approximately 10 m in diameter. Studies have confirmed the feasibility ofthis solution: the inter-axial distance between cells (between 22.5 m and 24 m as indicated in section5.3.3.2) is sufficient. The chamber is approximately 7 m high; its mechanical stability is provided by5 m bolts and lining thicknesses of 1.40 m. Another solution would consist of gradually turning thecontainer at the same time as it engages in the head of the cell. This solution would reduce the size ofthe civil engineering structures. An initial study has enabled the feasibility of this second solution tobe established.Figure 5.3.13Access drift for type CU1 or CU2 spent fuelAs for access drifts to type C cells, the geotechnical dimensions have been calculated for a minimumlifetime of a hundred years and take into consideration thermal effects which represent approximately40% of the stresses on the lining. The lining is dimensioned and constructed so as to minimise itsthickness. In its current section it is not reinforced [65].5.3.3.2 Dimensioning of cellsThe dimensioning of the cells takes the following into account: choice of materials and characteristicsof the clay buffer, dimensional stability of the sleeve and metal lining. The cell’s thermaldimensioning governs the spacing between packages and between cells.The specific characteristics of the spent fuel cell that influence the thermal and mechanicaldimensioning are as follows :- the heat transfer of spent fuels reduces more slowly than that of type C waste,- the presence of the buffer changes the near-field thermal behaviour (see below),- the presence of the buffer leads to the insertion of a large diameter metal lining,- finally type CU1 spent fuels have a greater diameter, which has repercussions for all radialdimensions of the cell’s components; it leads to greater sleeve and lining thicknesses.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM242/495