Tome Architecture and management of a geological repository - Andra

7 - Spent fuel repository zone• Ultrasonic testing (UT)The ultrasonic testing consists of analysing the reflections of ultrasonic signals on the surface betweentwo metal parts welded together. Interpreting the reflected signals pinpoints some of the nonvolumetricfaults, such as pockets where there is no bonding because the structure of the metalremains unmodified.At the current stage this test is planned to supplement the radiographic test. Furthermore it candetermine the thickness of the metal whose structure has been modified by the weld.7.4 The disposal cellsThe disposal cell is a vertical, dead-end borehole with a swelling clay engineered barrier. It isdimensioned to take one single container of spent fuel.As in the case of the C waste package disposal borehole, the choice of layout and borehole depth isgoverned by the need to limit the statistical possibilities of intersecting minor sub-vertical andpotentially water-conducting fractures.Figure 7.4.1View of a spent fuel disposal cell7.4.1 Description of the disposal cellThe design of the spent fuel disposal cells is very similar to C waste ones. However they differ in thatthere is no metal sleeve between the disposal package and the engineered barrier. This is because theproximity of an element in steel and the copper canister is likely to create galvanic corrosionconditions that could alter the canister’s durability.Thus the disposal package is emplaced directly in contact with the engineered barrier.Dossier 2005 granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY209/228