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A presentation at the MICE Video Conference on Wednesday the 5 th of May 2004

A presentation at the MICE Video Conference on Wednesday the 5 th of May 2004. Response to the Safety review comments. by Wing Lau -- Oxford. Safety Review Panel – Main Points – status review. Hydrogen Gas Handling & Venting system

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A presentation at the MICE Video Conference on Wednesday the 5 th of May 2004

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  1. A presentation at the MICE Video Conference on Wednesday the 5th of May 2004 Response to the Safety review comments by Wing Lau -- Oxford

  2. Safety Review Panel – Main Points – status review • Hydrogen Gas Handling & Venting system • Remove buffer tank and vent the hydrogen out directly - implemented • Remove relief valves in the hydrogen vent lines and have burst disks only – retained • Completely separate vent system for the absorber and vacuum spaces -implemented •  Detail specification of the Relief valve – work in progress • Is hydrogen detector appropriate in the vacuum line – still under consideration • Hydrogen detectors are needed in the ventilation system and in the personnel space around the experiment – will be implemented •  Examine the level to which piping should be Argon jacketed – will be addressed •  Replacing the flame arrestor with a vent pipe with an inert atmosphere - implemented •  Adopt Fermilab requirement vacuum system volume 52x H2 liquid volume – not implemented

  3. Safety Review Panel – Main Points • R & D on the Metal Hydride system • The use of hydride system requires active control. • The panel suggested a scaled model test. • It also asked the group to examine the safety issues associated with this system • R&D proposal defined and submitted

  4. Safety Review panel – Additional Points • Practicality of using intrinsically safe electrical equipment – response already drafted • Pipe joints – will be as requested • Detection of Hydrogen in Personnel areas – agreed • Attention to Interlocks, alarms and control system - ongoing. • Continuation of HAZOP assessment – agreed • Response to Absorber system leak scenario - ongoing • Potential of liquid hydrogen sloshing in warmer part of the feed pipe – to be addressed in level control. • Leak between the helium and hydrogen compartment in Absorberunit - ongoing

  5. Here is the final version of the report –printed in Powerpoint format for the purpose of this presentation, but will be in MS WORD format in the actual report.

  6. 3 main comments made by the Review Panel

  7. 11 further safety issues recommendations by the Review panel

  8. Appendix 1 ----- Buffer Volumes • Original Design • One evacuated buffer volume for both absorber and vacuum space venting • Separated from volumes by relief valves • Assessment from the review • Buffer volume is more effective if directly connected • Vacuum space • RAL safety does not require 12 x volume for vacuum space around absorber • Current design gives ~ 8 –10 x volume • Absorber volume • Design includes buffer volume in the absorber line • Window protection – response time • Simplification of control

  9. Appendix 2 ---Changes in MICE hydrogen system • In summary the AFC Safety Review Panel recommendations are implemented: • Original buffer vessel is removed • Vent manifold is added. The manifold is filled with nitrogen. • Venting lines are separated. • Other changes: • Buffer vessel is added in between absorber vessel and hydride bed. • Ventilation system is removed. Most of the equipment is now sits • under hydrogen extraction hood.

  10. P P P P P P H2 Gas bottle H2 Detector H2 Detector H2 Detector P P P P VP VP VP VP Version: 21/11/2003 Appendix 2--Hydrogen systembaseline layout Vent outside flame arrester He Purge system Metal Hydride storage unit (20m3 capacity) 1 bar Chiller/Heater Unit 18 K He 14 K He from Cold box Fill valve X 2 X 2 1.6 bar 2.0 bar Purge valve Liquid level gauge Vent outside flame arrester Vacuum Ventilation system Internal Window LH2 Absorber Safety window Purge valve LHe Heat exchanger Vent outside flame arrester Evacuated vent buffer tank 2.0 bar Vacuum vessel 1.6 bar 1.4 bar Pressure relief valve Pressure regulator Non-return valve Pressure gauge Vacuum pump Valve Bursting disk

  11. P P P P H2 Detector H2 Detector P P P P P P P P P Appendix 2--Hydrogen systemrevisedbaseline layout High level vent High level vent Vent outside flame arrester Non return valve Vent manifold Vent manifold 0.1 bar Hydrogen zone 2 Extract hood VP2 PV8 P1 Metal Hydride storage unit (20m3 capacity) PV7 Chiller/Heater Unit PV2 PV1 Tbed PV3 1 bar Tchill Buffer vessel PV4 1 m3 Fill valve HV1 18 K He out 14 K He in Zone 2: An area within which any flammable or explosive substance whether gas, vapour or volatile liquid, although processed or stored, is so well under conditions of control that the production (or release) of an explosive or ignitable concentration in sufficient quantity to constitute a hazard is only likely under abnormal conditions. 0.5 bar P2 0.9 bar Hydrogen supply HV2 Purge valve P3 Windows: Design pressure 1.6 bar abs Test pressure 2.0 bar abs Burst pressure 6.4 bar diff Purge valve Absorber window HV3 Tabs 0.9 bar Safety window Nitrogen supply PV6 Helium supply 0.5 bar VP1 Pressure relief valve Non-return valve Pressure gauge Pressure regulator VP Vacuum pump Valve Bursting disk

  12. Appendix 3 --- R&D programme on metal hydride storage system • Conceptual question: a small-scale rig vs. a full-scale prototype ? • Decision: go for a full-scale system which later will be used in MICE. • R&D goals: • Establish the working parameters of a hydride bed in the regimes of storage, absorption and desorption of hydrogen. • Absorption and desorption rates and their dependence on various parameters such as pressure, temperature etc. • Purity of hydrogen and effects of impurities. • Hydride bed heating/cooling power requirements. • What set of instrumentation is required for the operation of the system? • Safety aspects including what is the necessary set of safety relief valves, sensors and interlocks. • Status • Programme on hold pending funding approval for 2004/05

  13. Appendix 4 --Hydrogen level control – design considerations • Level Control – what variations do we need to respond to: • Level will vary due to temperature changes in the absorber • Variation in density of LH2 could give ~ 1 – 2 liters volume change • Such changes cannot be accommodated in small pipes • 25mm dia = 2.2m/liter • Such level changes will be relatively slow under normal operating conditions • Energy to go from 14 – 18K ~ 50kJ for 20 liters • Nominal heat load /absorber is few W • Time 14 – 18K is ~ 5 – 10 hrs • Most significant effect will be intermittent gas boil off due to changes in level – especially so for the horizontal pipe

  14. Appendix 4 ---Hydrogen level control – design considerations • Level Control – Where is best place to monitor/control level • Absorber neck tube • Insufficient volume • Horizontal pipe • Not practical • Vertical pipe • Need to thermalise the horizontal pipe • Small volume available • Main absorber volume • Ullage - 2 liters is 10% • Temperature of absorber body will be uniform • Increase in volume will cause very little boil off • Less active role for control system – hydride bed • External buffer volume 1m^3 could absorb ~ 0.5 –1 litre before activating the relief system – assuming no return to the hydride bed - need further work

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