Architecture and management of a geological repository - Andra

5 – Repository ModulesFinally, it should be noted that the Yucca Mountain concept, due to the forced ventilation runningthrough the drifts in which the packages are disposed, has limited similarity with the other concepts.Furthermore, the environmental conditions in which the packages are disposed are different, as thehost geological formation is not saturated.5.3.3 Description and dimensioning of CU1 and CU2 modulesThis section describes the CU1 and CU2 modules. CU3 modules do not have clay engineered barriersand are in principle identical to those described for type C waste in section 5.2.5.3.3.1 Description of the cell and access driftThe description below emphasises the specific features of the spent fuel cell. The features in commonwith the type C waste cell are described in brief.• Description of the cellThe cell, as designed at this stage of the studies, is a tunnel closed at one end, around 3.3 m indiameter in the case of the CU1 cell and around 2.6 m in diameter for the CU2 cell.In the usable part destined to receive the packages, the cell consists of three components: a steel lining,a swelling clay-based engineered barrier with a radial thickness of 800 mm, and a permanent metalsleeve (maintained after closing). The sleeve facilitates the positioning or withdrawal of packages.The top of the cell is designed to receive a seal. The latter consists of a clay plug and a concreteretaining plug. The peripheral parts of the retaining plug (clay and concrete) are positioned after theswelling clay buffer, before the packages. The central space allows the packages to pass and to thisend receives a temporary sleeve, removed in order to close the cell.Figure 5.3.10Longitudinal section through CU 1 cellDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM239/495