Architecture and management of a geological repository - Andra

Figure 10.3.23Cage with Vibrating Wire Extensometers10.3.12.2 The evolution of the shaft observation system after the shaft is sealedThe structure sealing works include the removal of the lining at the location of the seal. Themonitoring equipment is therefore also removed. The sealing operation does not affect the lifetime,nor the reliability of the monitoring equipment outside the sealing zone. The measurements madedownstream (on the surface) can therefore be continued and transmitted to the surface. The upstreammeasurements (deep side) can, during a transitional period, be transmitted by wireless equipment (seeparagraphs 10.3.5.3 and 10.3.7.4). If it were decided to seal one particular shaft before the others,these measurements could also be transmitted through one of the shafts that are still accessible. Itshould be noted that in all cases, it is possible to install monitoring equipment in two sections(upstream and downstream) of the seal, without significantly affecting its long-term hydraulicperformance.10.3.13 Conclusion regarding the contribution of observation to the reversible repositorymanagement processThe observation of the structures and in particular the cells enhances the phenomenological evolutionof the repository process. It allows us to quantify the parameters which characterise each stage of theprocess, provides a reassessment of the lifetime of cells and specifies the information required toevaluate the conditions for possible retrieval of the disposal packages. All this information contributesto the underpinning of the decision to proceed from one stage of the repository process to the next withobjective scientific and technical data. In the case of B cells, the observation enables us in particular totrack the mechanical evolution of the lining upon which the lifetime of the cells depends. It also makesit possible to quantify the gases produced by the waste and to understand the conditions of a possibleretrieval of the packages.In the case of C waste or spent fuel disposal cells, the observation enables tracking of the thermal fieldcreated by the exothermicity of the packages and the verification of its mechanical incidence. It alsopermits tracking of phenomena such as the resaturation level or the composition of the atmosphere inDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM418/495