MICE Hydrogen System Implementation Tom Bradshaw Elwyn Baynham Iouri Ivaniouchenkov Jim Rochford

Talk Contents Design Criteria – what is the conceptual basis for the design Baseline layout Specification for the hydride beds Safety containment Pipework and implementation Thermal issues

Design Criteria Independent systems on each of the absorbers to eliminate consequential effects –This will also ease the staging of MICE and reduce the need for extra testing –Easier to isolate faults –Smaller systems are easier to deal with

Design Criteria (2) Minimise venting and purging –Most accidents have happened during venting operations –Sealed system is safer – we have quite a large amount of hydrogen 3 x 22 litres of liquid Minimise amount of hydrogen

Design Criteria (3) Must be safe in the event of a power loss or system shut-down No surfaces below the BPt of Oxygen – this is to prevent cryopumping of oxygen on any surface that may come into contact with hydrogen in the event of a failure Safety volumes to contain gas, relief valves to prevent back flow in case of catastrophic release Prove a system for a neutrino factory

Baseline layout 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 Internal Window 70 K Safety window H 2 Gas bottle P P Fill valve Metal hydride hydrogen storage unit (20 m 3 capacity) Vent outside flame arrester He 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 H 2 Detector Ventilation system Vent outside flame arrester Chiller/ heater unit

Pipe sizes Specific load (W/cm2)3.6 Load (W) Safety factor x2 (W)

Absorber properties Liquid-hydrogen volume (at 20K), litres21 Hydrogen volume (at STP), litres16548 LH2 operating temperature, K18 LH2 operating pressure, bar abs1.2 LH2 max pressure, bar abs1.7 LH2 min pressure, bar abs1.05 Max. heat removal, W100 Refrigerant mass flow, g/s<2 Refrigerant inlet (outlet) temperature, K 14 (18) Refrigerant inlet (outlet) pressure, bar 18(14) Absorber vacuum volume (within the module), litres91

Hydride Bed Parameters Preferable size<1 m 3 Environment temperature15-25 °C Operating pressure in the system, bar abs1.2 Max. pressure in the system, bar abs1.7 Min. pressure in the system, bar abs1.05 Hydrogen storage capacity (at STP), litres20000 Absorber filling/empting time, hours5

Safety Containment All external hydrogen pipes will be coaxial with an Argon jacket Hydrides and gas handling system will be situated under a hood

Layouts – Pipework Use co-axial lines to prevent hydrogen escaping into the hall Storage and buffer tanks located in a vented enclosure Hydrogen pipes are at a high level so that any flames or escaping gas does not pass any personnel

No surfaces below Bpt O 2 Model run with 10 layers of MLI on inner surfaces and thermal isolation as shown Thermal models used to verify the temperatures of the outer window in normal operation.

No surfaces below Bpt O 2

Implementation Absorbers will be tested prior to installation (see accompanying presentation) When in place helium leak detection will be used to check the leak tightness of the system prior to filling with hydrogen

Implementation Hydrogen sensors will be fitted in appropriate areas in the laboratory Intrinsically safe electrical connections will be made to all parts of the hydrogen system User and operating manual, procedures will be developed for the safe operation. A training plan will be developed

Summary We have well defined criteria for the current design of the hydrogen system Areas of risk have been identified and removed in the design Inherently safe system that will passively reach a stable state without operator intervention

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