MICE Safety System DE Baynham TW Bradshaw MJD Courthold Y Ivanyushenkov

Scope MICE hazards and solutions Hydrogen control and safety system MICE safety system

MICE Layout

MICE Phase I initial

MICE Phase I final

MICE Hazards Beam Radiation Fire Explosion Overpressure Material brittleness Skin burn Radiation HV=> Sparks HV RF LH 2 TrackerLH 2 Tracker Particle detectors High magnetic field => High mechanical forces Magnetic stray field Photo detectors and front-end electronics Optical fibres Photo detectors and front-end electronics Optical fibres HV TOF

Beam Radiation RF LH 2 TrackerLH 2 Tracker Radiation Particle detectors Radiation safety is achieved by: - shielding the beam line; - no access to the experimental hall when RF power is on; - local shielding of some bits of cryogenics equipment such as control electronics, cold boxes and valve boxes; - local shielding of detectors front-end electronics MICE Hazards: Solutions

Beam RF LH 2 TrackerLH 2 Tracker Particle detectors High magnetic field => High mechanical forces Magnetic field safety is achieved by: - passive magnetic shielding of both the MICE control room and the ISIS linac (brings magnetic field down to below 5 gauss-level in the public areas outside the experimental hall); - restricted access to the experimental hall. High mechanical forces on the MICE components are: - being analysed and understood ; - taken into the account in the MICE design. MICE Hazards: Solutions (2)

Beam RF LH 2 TrackerLH 2 Tracker Fire Explosion Overpressure Material brittleness Skin burn Radiation HV=> Sparks HV Particle detectors Hydrogen safety is achieved by: careful design of the hydrogen absorber : - FEA analysis of the windows (confirmed by tests); - avoiding cold surfaces where air might be plated; - a double barrier between hydrogen and air. careful design of the hydrogen system: - a closed system concept keeps hydrogen venting at the minimum; - hydrogen is stored as a solid compound in a hydride bed; - passive pressure relief system is implemented; - hydrogen zone is localised; - ignition sources are kept outside hydrogen zone. certification of all materials tests of sub-assemblies and assemblies test of complete system MICE Hazards: Solutions (3)

Instrumentation Pressure gauge Non-return valve - P P VP Vacuum pump Bursting disk Pressure relief valve Valve Pressure P Chiller/He ater Unit Helium supply Hydrogen supply P Nitrogen supply P P 1 m 3 P - P P VP Vacuum pump Bursting disk Pressure relief valve Valve Pressure regulator Coolant Out (20m 3 capacity) Metal Hydride storage unit (20m 3 capacity) P PP VP02 VP01 Heater / Chiller 1 bar diff PPPP Helium supply Hydrogen supply Extract hood P Nitrogen supply PP P P 1 m 3 Vent manifold PG01 RV06 PV01 PV18 PV03 PV05 PV07 PG03 P PG02 PV20 Test absorber module In Absorber volume 0.5 bar diff 0.9 bar diff PV19 CV04 CV17 RV10 BD09 HV bar diff RV bar diff BD12 HV11 PV14 High level vent Non return valve 0.1 bar RV21 Buffer vessel PV15 PP PV02 Argon jacket T TS3 T T TS1 Temperature sensor H2

Control logic – Fill Sequence Chiller on Set TS1_sp = TS1_initial PV2,3,5,7,14,17,18,19 closed CV4 closed PV1 open VP2 on, PV20 open Cooling System on Set TS2_sp = 15K Start Pressure Control Loop Start Vac Monitor Open PV2,3 Open CV4 TS1<TS1_sp And VG3<1mbar PG1  PG1_sp Close PV2&3 and CV4 Stop Pressure Control Loop Set TS1_sp = TS1_low Open PV5 LS1 > LS1_sp H2 System Ready Increment/Decrement TS1 Empty Sequence VG3<1mbar Vac monitor Pressure Control Yes No Yes No Yes No Note: ***_sp - set point

Empty Sequence Open PV7 Close PV2,3,4 Set TS1_sp = TS1_low Set TS2_sp = 20K Stop cryocooler Start Absorber Heater Control Loop LS1<LS1_low Empty Sequence Yes No Close PV1 PG2<0.1bar AND TS3>100K H2 System Empty Yes No 1bar<PG2<1.3bar Increment/Decrement TS3 Absorber Heater Control Yes No Stop Absorber Heater Control Loop TS3>30K Yes No

Helium Purge Sequence VP1 On Close PV1,14,17,18,19 Open PV2,3,5,7 Open CV4 100% Close PV19 Open PV18 Open CV4 5% to control flow VG5<1mbar H2 System Purged Purge Sequence No Open PV19 Yes 1bar<PG1<1.3bar AND 1bar<PG2<1.3bar Close PV19 Open PV18 Open CV4 5% to control flow VG5<1mbar No Close PV18, Open PV19, Open CV4 100% Yes 1bar<PG1<1.3bar AND 1bar<PG2<1.3bar Close PV19 Open PV18 Open CV4 5% to control flow VG5<1mbar No Close PV18, Open PV19, Open CV4 100% Yes 1bar<PG1<1.1bar AND 1bar<PG2<1.1bar Yes No Close PV18

MICE DAQ and Control System

Interfaces Hydrogen system MICE Safety system Hardwired status signals: ready (for use) / not ready, fault, H2 leak, H2 being vented PSI Solenoid Linde Fridge Fridge Ready (and in use) Fridge Ready Solenoid Powered Solenoid Quenched Solenoid Current Ramping 3 Signals from solenoid Fire alarm, power cut