Preliminary Risk Analysis of the LHC Cryogenic System (CERN-LHC-Project-Report-324)

The Large Hadron Collider (LHC), presently under construction at CERN, will require a helium cryogenic system unprecedented in size and capacity, with more than 1600 superconducting magnets operating in superfluid helium and a total inventory of almost 100 tonnes of helium. The objective of the Preliminary Risk Analysis (PRA) is to identify all risks to personnel, equipment or environment resulting from failures that may accidentally occur within the cryogenic system of LHC in any phase of the machine operation, and that could not be eliminated by design. Assigning a gravity coefficient and one analyzing physical processes that will follow any of the recognised failure modes allows to single out worst case scenarios. Recommendations concerning lines of preventive and corrective defence, as well as for further detailed studies, are formulated.