MICE AFCSWG Safety Review Summary Mary Anne Cummings Dec. 17, 2003 MICE Video Conference

The Review Last week (Dec 9-10) we had our first formal review of the safety issues involved in the MICE experiment at LBL The Review Committee: D. Allspach (FNAL) G. Benincasa (CERN) M. Seely (Jlab) L. Starritt (NASA/WSTF) J. Weisend (SLAC) Chair J. Wells (RAL) MICE AFC Safety Issues: Hydrogen: Flammability, detonation, low temperature, O 2 cryopumping, large liquid-gas expansion ratio RF cavities: Dark currents, Be windows Magnets: Large fringe fields, quenching Topics: Magnets M. Green Detectors A. Bross LH2 Absorber M. A. Cummings Magnetic forces J. Rochford LH2 System E. Baynham R & D, testing, certification W. Lau RF System D. Li Hazard Summary E. Baynham

The LH 2 Issues Compact structure of the cooling channel means the absorber and LH 2 system have to be designed with all other components and safety hazards in mind For safe operation, have designed with the redundant requirements: 1)LH 2 and O 2 separation 2)The avoidance of any ignition sources in contact with hydrogen. The four key features of the design with respect to safety are: 1)Window thicknesses specified based on safety factors of 4.0 for the absorber and vacuum windows at maximum allowable working pressure (MAWP). Vacuum windows required to withstand 25 psi outside pressure without buckling. 2)Two layers of shielding between the outside atmosphere and the LH 2 ; the outer surface at room temperature to minimize the freezing of O 2 on the absorber- system windows. 3)Separate vacuum volumes provided for the RF cavities, magnets, and LH 2 absorbers. 4)Hydrogen evacuation systems using valved vents into external buffer tanks.

Accommodating LH 2 1.Sufficient clearance for LH 2 venting into evacuation tanks (21 liters liquid  liters at STP) 2.RF: Window provides spark barrier; vacuum between RF and LH 2 vacuum vessel 3.LH 2 -Air flammability limits: 4-75% ; detonability limits 18-59%  conventional seals and vacuum vessels can provide sufficient barriers between them. 4.All safety interlocks mechanical – based on expeditious venting of LH 2 into evacuation tank RAL safe LH 2 operation

Absorber coil system Ambient temperature on vacuum shields and outer channel wall Quench force on windows is small Static forces are decoupled from the LH 2 absorber Heat from quench and static sources are insufficient to cause boil-off Clearance for possible LH 2 rupture into vacuum volume sufficient to prevent cascading window rupture Absorber Vacuum Volume: Magnet bore Large end plate Absorber Window: Vacuum Window: He inlet: Outer wall

LH 2 System Safety and design considerations: Hydride bed storage option Safety containment/Hydrogen Zones Pipework and implementation Interlocks: evacuation system and burst disks Heat and temperature Ventilated Hood Absorber vacuum Lab Outside

Experiment certification Window certifications Absorber pre-assembly and testing Absorber/coil assembly, testing and certification Assembly into MICE cooling channel and certification Hydrogen fill LH2 absorber Coil assembly Transverse absorber/coil removal from channel Metal hydride beds with buffer tanks

Off-normal conditions 1)RF cavity vacuum or detector vacuum air leak 2)Absorber vacuum window leak 3)Absorber leak 4)Hydrogen freezing 5)Large heat leak to the absorber 6)Loss of refrigeration or loss of electrical power 7)Quench of the focusing solenoid 8)Rupture of the hydrogen window 9)Rupture of both hydrogen and safety windows Exception handling for LH 2 : Expeditious H 2 evacuation (relief valves, pumping) MICE shut-down Hydride bed temperature regulation Magnets: passive shielding; restricted access; forces analysized and structurally accommodated RF: shielding of beamline, cryo equipment and detector electronics; water valve interlock; restricted access Safety design based on recovery from 2 independent system failures Off-normal conditions, LH 2 :

Review Outcome Unqualified success: Positive first review: no show-stoppers or omissions Excellent advice and feedback Detailed suggestions for development in three areas: Gas-handling and venting R & D of the metal hydride system Windows development (seals, monitoring) Good discussion on interlocks and monitoring Instructive discussion of “instrinsically safe” and proper response thresholds for off-normal conditions Can now proceed with the technical design