Architecture and management of a geological repository - Andra

11 – Operational SafetyHowever, with a slow evacuation speed (0.5 m/s), personnel would quickly be caught up by smoke,with a mean opacity of around 0.6 m -1 , or a visibility distance reduced to 2 m. In this case, personnelmay have to wear their individual breathing apparatus for the final few metres before reaching theinterconnecting drift.11.4.2.2 Fire with smoke layeringThe example used is that of machinery with a thermal power of 30 MW in a connecting gallery. Thiscase, which corresponds to a fire involving heavy construction machinery, is an envelope casecompared with that of a package transporter which would have a lower thermal power (15 MW).The propagation, height and temperature of the layer of smoke were determined analytically, usingknowledge of stratification phenomena observed in the case of road tunnels. The effects associatedwith radiation emitted by the smoke from the fire are comparable with the permissible threshold forthermal effects on humans (2 kW/m² for persons not equipped with protection 172 ).The results of simulation (see Table 11.4.1) show that escaping personnel are subjected to a maximumheat radiation level of 0.9 kW/m² after 100 m in the case of an evacuation at the slower speed(0.5 m/s), which corresponds to satisfactory conditions.Table 11.4.1Heat radiation received during evacuation in the case of a fire (30 MW) withlayered smoke in a connecting driftHeat radiation received by personnel (kW/m²)Speee of personnelmovementLocation withrespect to seat of fire0.5 m/s 1 m/s100 m 0.88 kW/m² 0.38 kW/m²200 m 0.56 kW/m² 0.38 kW/m²400 m11.4.3 ConclusionThe smoke does not reach thisdistance due to the starting ofthe smoke clearance system0.36 kW/m²In underground repository installations, two types of fire can develop: fires with smoke layering (inconnecting drifts) or smoke de-layering (in access drifts to type C or spent fuel waste cells). In bothcases, simulations conducted tend to indicate that the design of the underground infrastructure, withclusters of parallel drifts connected at regular intervals by interconnecting drifts, enables personnel toescape from the location of the fire under satisfactory conditions, quickly reach a parallel driftsupplied with fresh air (clear of the smoke circuit) then return to the surface under good conditions.In a few cases (fire with smoke de-layering and slow evacuation speed) it cannot be excluded at thisstage that the smoke might catch up with the escaping personnel and that they may have to use theirpersonal breathing and eye protection.172 This radiant rating corresponds to a maximum smoke temperature of around 200°C, wich would induce an air temperature lower than80°C in the healthy zone (cf. Figure 11.4.3)DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM463/495