The update of the Preliminary Risk Analysis of the LHC Cryogenic System

The Preliminary Risk Analysis (PRA) of the Large Hadron Collider cryogenic system, performed in 1998, was aimed at the identification of all the risks for personnel, equipment or environment caused by the failures that might accidentally occur in any phase of the machine operation, and that could not be eliminated by design. The risk analysis was performed during a design and an early construction phase of the machine, so after the collider commissioning and consolidation experience, especially due to the 080919 incident in the LHC sector 3-4, PRA had to be revised and updated. This note gives the overview of the redefined or updated data. It discusses the criterions of cryogenic failures categorization taking into account their occurrence and severity.