Conclusion on the helium spilling experimental program: cryogenic failure consequences on the LHC tunnel

by Maciej CHOROWSKI (AT Division and Wroclaw University of Technology)

Thursday 20 Mar 2003, 14:15 → 15:15 Europe/Zurich

AT Auditorium (CERN)

The Large Hadron Collider will contain more than 95 tons of liquid and supercritical high-density helium. Some potential failures of the LHC cryogenic system might be followed by helium discharge into the tunnel and as a consequence the oxygen concentration might decrease below the safe level of 18% or ambient temperature might drop significantly. For safety reasons it is important to recognise all processes and phenomena following cold helium discharge. In order to investigate the helium propagation in the LHC tunnel, a dedicated test-tunnel has been designed and built. It has been equipped with controllable air ventilation and helium relief systems enabling the simulation of different scenarios of cryogenic installation failures. It was also possible to modify the basic construction of the test-tunnel by adding special modules in order to investigate the presence of the LHC accelerator inside the tunnel, the tunnel enlargements and the influences of the LHC tunnel elevation. Helium-air mixture flows corresponding to different initial conditions of ventilation air and discharged helium have been observed. Characteristic patterns of mixture flows have been identified. Flow-pattern, shape of measured oxygen and temperature profiles have been analysed for different tunnel elevations and with the tunnel enlargements and the accelerator mock-up. The results have been scaled to the LHC conditions with respect to each sector peculiarities (elevation, ventilation, and enlargements).