Tracking the Helium Balance in FREIA

In the FREIA laboratory at Uppsala University we test the super-conducting spoke-cavities for the European Spallation Source. Liquid Helium for cooling the cavities is provided by a liquefaction plant from which also a local user community at the University is served. Recently we encountered a leak due to a faulty valve which went undetected for some time and caused significant loss of Helium. In order to prevent such mishaps in the future we implemented a Helium tracking system that includes detailed accounting of Helium leaving and entering the closed system as well as all volumes containing Helium in the system. We describe the technical implementation and experience to date.