Architecture and management of a geological repository - Andra

11 – Operational SafetyTotal power (MW)353025201510500 10 20 30 40 50 60 70 80 90 100 110 120Time (mins)Figure 11.4.1Standard total thermal powerfor a 30 MW fire11.4.1.2 How fires developIn an underground environment, fires emit smoke as they develop which spreads throughout the drift(fire with smoke de-layering) or forms localised pockets at the top of the drift (fire with smokelayering) depending on the ventilation conditions encountered.• Fires with smoke de-layeringFires with smoke de-layering give off smoke which gradually spreads through the drifts, turning theatmosphere opaque, and often hindering the evacuation of personnel. This type of fire, produced whenthe air speed in the drift is greater than 1 m/s, is characterised by a uniform mixture of air and smokethroughout the drift’s cross section at a given distance from the fire.In the case of a repository, fires in type C waste and spent fuel disposal cell access drifts, ventilated byan inflow of fresh air throughout the drift’s cross section, and exhausting the smoke via a smokeclearancevent at the end of the operational unit, would be of this type.For this type of fire (see Figure 11.4.2), personnel preferably escape by heading towards theconnecting drift supplied with fresh air. If this is not the case, personnel downstream of the fire canhead for the first interconnecting drifts in order to reach the adjacent access drift supplied with freshair (with a maximum distance of 200 m to be covered thanks to the layout of the interconnectingdrifts) then into the connecting drift.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM458/495