High Pressure Source/Cryostat Relief Solutions

This report addresses solutions to the potential problem of cryostat over pressurization by the nominal 65 psi MWAP LAr source dewar. Uncontrolled (by reason of failure) filling of a 15 psi MW AP cryostat by the LAr fill line could cause over pressurization by overwhelming the provided cryostat relief system. Three levels of protection against over pressurization by the source dewar are mentioned in this report; the reduced (operational) relief pressure, the source pressure regulator, and the LAr dewar cooling loop. Only the first of these is recognized by the ASME code as sufficient protection, the others provide operational convenience and avoid the loss of detector fluid. Flow limiting device solutions are not considered because of the conflicting requirement to empty and fill the cryostats rapidly (within one eight hour shift), e.g. the movement of the cryostat from the assembly hall to the collision hall, or the inverse operation