1. 1 MICE Absorber working group meeting @ Columbia, 13 June 2003 MICE Hydrogen System. Preliminary HAZOP. Elwyn Baynham, Tom Bradshaw and Iouri Ivaniouchenkov, RAL

2. 2 MICE Absorber working group meeting @ Columbia, 13 June 2003 PP VP Vacuum pump Bursting disk Pressure relief valve Valve Pressure regulator Pressure gauge 18 K He to Compressor via Radiation shield 14 K He from Cold box Liquid level gauge LH 2 Absorber Vacuum Vacuum vessel LHe Heat exchanger 12 litre Buffer tank Hydrogen flow and safety system Internal Window 70 K Safety window H 2 Gas bottle P P Fill valve Hydrogen tank Volume: 11 m 3 Pressure > 0.1 bar Vent outside flame arrester He / N 2 Purge system Non-return valve Vent outside flame arrester Vent valve 1.7 bar 2.1 bar H 2 Detector P P P P Evacuated vent buffer tank Volume: VP P X 2 VP Version: 09/06/2003 Hydrogen module enclosure (igloo) H 2 Detector Ventilation system Vent outside flame arrester

3. 3 Node 1: Hydrogen tank Intent: To keep hydrogen gas in the tank-hydrogen vessel closed system. NoParameterGuide word CauseConsequenceSafeguardsRecommendations 1PressureLower1. Tank is leaking. 2. Pipe is leaking. 3. Absorber vessel is leaking. 1. Air can leak in the tank and in the hydrogen vessel and an explosive mixture can be formed. 2. Hydrogen is leaking out in the experimental hall. 3. Hydrogen is leaking into vacuum jacket. Pressure gauge to trigger an alarm. Hydrogen ventilation system collects and vents hydrogen out. Hydrogen detector to trigger an alarm. Implement an active pressure gauge. Implement ventilation system. Implement an active hydrogen detector. 2PressureHigher - Fill valve is accidentally open - Tank is overheated Tank can brakePressure relief valve to vent outside. Implement a pressure relief valve. MICE Absorber working group meeting @ Columbia, 13 June 2003

4. 4 Node 2: Hydrogen absorber internal vessel with hydrogen windows. Intent: To keep hydrogen liquid inside hydrogen absorber module. NoParameterGuide word CauseConsequenceSafeguardsRecommendations 1TemperatureLowerToo much cooling power from the He cooling system. 1. Pressure in the hydrogen system drops. 2. LH2 level in hydrogen vessel rises. Pressure gauge to trigger an alarm. Liquid hydrogen level meter to trigger an alarm. Implement an active pressure gauge. Implement an active liquid level meter. 2TemperatureHigher1. Not enough cooling power from the He cooling system. 2. Power cut. 1. Liquid hydrogen evaporates and LH2 level goes down. 2. Pressure rises. Pressure gauge to trigger an alarm. Liquid hydrogen level meter to trigger an alarm. Implement an active pressure gauge. Implement an active liquid level meter. 3PressureLower1. Window is leaking or broken. 2. Pipe is leaking. 3. Hydrogen tanks is leaking. 1. Hydrogen leaks into vacuum vessel. 2. Hydrogen is leaking out. Hydrogen detector to trigger an alarm. Hydrogen ventilation system collects and vents hydrogen out. Implement an active hydrogen detector. 4PressureHigherTemperature is increased. Windows can break. Pressure relief valve to dump hydrogen into a buffer tank Implement a pressure relief valve and a buffer tank.

5. 5 NoParameterGuide wordCauseConsequenceSafeguardsRecommendations 1PressureHigher - Hydrogen window broken - Vacuum pump failure Hydrogen bursts into vacuum jacket Pressure relief valve to dump hydrogen into buffer tank Node 3: Hydrogen absorber vacuum jacket with safety windows. Intent: - To insulate thermally the internal hydrogen vessel. - To provide additional barrier for air. MICE Absorber working group meeting @ Columbia, 13 June 2003

6. 6 Node 4: Buffer tank. Intent: To quickly relief pressure in the absorber module in case of window burst. NoParameterGuide wordCauseConsequenceSafeguardsRecommendations 1PressureHigher - Hydrogen comes from absorber module - Vacuum pump failure Pressure relief valve to dump hydrogen outside MICE Absorber working group meeting @ Columbia, 13 June 2003

7. 7 Node 5: Hydrogen module enclosure. Intent: To localize and vent hydrogen in case of hydrogen leak. NoParameterGuide wordCauseConsequenceSafeguardsRecommendations 1Hydrogen concentration Higher - Hydrogen leaks out absorber module - Hydrogen leaks out hydrogen pipes Explosive oxygen- hydrogen mixture can be formed Ventilation system to quickly vent hydrogen out. Hydrogen detector to trigger an alarm and to start a high rate mode for the ventilation system. Implement ventilation system equipped with hydrogen detector. MICE Absorber working group meeting @ Columbia, 13 June 2003