Architecture and management of a geological repository - Andra

6 – Overall underground architecture6.4.4 VentilationThis section presents a possible organisation of ventilation that would provide health, safety and firefunctions.The tree structured architecture involves the construction of long dead ends (up to several kilometers).This geometry entails very significant aerolic head loss which is taken into account in the design of theventilation system.6.4.4.1 Design principles• General design of the ventilation of the underground installationsThree main design principles for the ventilation of the underground installations were retained :A primary ventilation circuit using blowers located on the surfaceAir is circulated in the underground installations mainly by fans located on the surface: fans blowingair at the head of the personnel transfer and service shafts and exhaust fans sucking air at the head ofthe air exhaust shaft. This arrangement ensures that the fresh air entries are always overpressurisedwith respect to the air returns or the smoke removal shaft.A full section air intake and an air exhaust in a duct or in a dedicated air driftThe incoming fresh air sweeps over the entire section of the underground drifts without a dedicatedduct. This applies to both the drifts connected to the nuclear operation and the drifts dedicated to theconstruction activities.Air exhaust and smoke removal are accomplished through ducts located in the crown of the drifts or,when the size of the vehicles circulating in the drifts is incompatible with the presence of ducts, inventilation drifts exclusively dedicated to these functions.Figure 6.4.4 and Figure 6.4.5 show these principles of ventilation. In normal operation, the fresh aircirculates up to the end of the drifts to be ventilated and then the air is returned from the end. In caseof a fire, the smoke can be sucked up by several traps ensuring a redundancy for the smoke removalsystem.Figure 6.4.4 Operating principle ofventilation with air exhaust in a ductFigure 6.4.5 Operating principle of a smokeremoval ductDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM274/495