Evacuation Modelling Of A Large Underground Cavern Of The CERN Accelerator Complex

Giordana Gai - CERN, European Organization for Nuclear Research


The contribution describes the evacuation analysis of a large underground facility, located at approximately 100 m of depth and part of the CERN largest particle accelerator complex: the Large Hadron Collider (LHC). The experiment, called ATLAS (A Toroidal LHC Apparatus), is mainly composed by two big caverns, connected among each other with corridors and passages and eventually connected to the surface with lifts, whose use is foreseen in the evacuation procedure. Given the complexity of the cavern from an evacuation standpoint, the use of agent-based modelling is employed. The evacuation model Pathfinder has been selected, and its capability to automatically integrate FDS toxicity data along the paths of the occupants and calculate their maximum Fractional Effective Dose (FED) has been used. The cavern also includes a particle detector, unique in its layout, for which the evacuation procedure foresees self-rescue masks to be collected at specific locations before moving towards the exit. Behavioural scenarios are carefully defined based on literature and evacuation drills. A number of evacuation simulations are run with Pathfinder adopting pseudo- random sampling from distributions to vary the model inputs and evaluate behavioural uncertainty. Depending on their initial position in the main cavern (total volume equal to 47000 m3), the occupants - likely to be involved in maintenance activities - would need to evacuate using scaffolding, ascending and descending stepladders and stairs. The case study shows the importance of using advance modelling techniques to properly evaluate the consequences to life safety during fire evacuation in complex underground facilities.


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