safety requirements and regulations 10/3/20121safety requirements & regulations james sears

Safety Requirements and Regulations

10/3/2012 1Safety Requirements & Regulations James Sears


Responsibility for safety oversight is carried out by safety committees within CLASSE and

by Cornell’s Department of Environmental Health and Safety (EH&S).



CLASSE has over four decades of experience designing, building and

collaborating on SRF and Cryogenic systems


Cryostat Safety Issues

Personal safety

&

Equipment protection


Cryostat safety issues

Oxygen deficiency hazard

Over pressurization


Oxygen deficiency hazardsNo Liquid Nitrogen used for cooling

Potential oxygen deficiency hazards will be mitigated by excluding liquid nitrogen from the tunnel and moving the

tunnel air at 400 feet per minute so that in the event helium is released, it does not pose a hazard to personnel spaces in the tunnel. In addition, only a limited amount of helium will

be present in the tunnel. Even if both helium return lines and the ventilation of the tunnel failed, loss of all the

helium contained in one of the linacs would only drop the oxygen availability by a maximum of 40 percent. While this does not satisfy the OSHA standard for 8 hour occupancy, it

will not cause loss of consciousness thus allowing any personnel in the tunnel to leave safely. 1

10/3/2012 Safety Requirements & Regulations James Sears

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Oxygen deficiency hazardsLiquid helium will be stored in the 640 meters of superconducting linac sections mounted in the

proposed looped tunnel. There will be a total of 64 crymodules, each approximately ten meters in length

and arranged end to end and divided between two cryogenically independent linacs. Each cryomodule

will have an inventory of 168 liters (44 gallons) of liquid helium for a total of 5,400 liters (1,420 gallons) of

liquid per linac. 1


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Over pressurization The inventory of helium which might be evaporated has

been minimized by compartmentalizing the helium inventory and designing each of the helium vessels surrounding the accelerating devices to be just large

enough to transport the heat generated in the accelerators and no larger. The pipes that will bring the helium to and

from the cryomodules have been sized so that the pressure generated by a sudden evaporation of helium will not overpressure them dangerously. Backup relief valves

will also be installed. 1


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Over Pressurization


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a. Over pressurization of Helium supply and return lines will be dealt with at the Cryo plant. There are no burst inside the MLC

b. Helium leaks into MLC. Pressure relief install on Standard 5.3”ID auxiliary port.

c. Accidental loss of insulation or cavity vacuum

Over Pressurization CLASSE is not a DOE lab and not subject to same stringent pressure vessel code rules but we are concerned about these requirements we are trying to design a system that will meet these codes. The MLC Module is based on the DESY XFEL design which was designed to meet European PED as well as ASME code. DESY XFEL model has approximately same helium inventory in one of vacuum section as one of Cornell's MLC modules, both are ~300 meters long.

DESY conducted a series of experimental test of fault condition during cryogenic operations2 so lets look at will look at their test for

a) Helium supply leak

b) Accidental loss of insulation or cavity vacuum


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XFEL testFor a realistic worst case scenario DN100 (4inch) flanges at the vacuum vessel and the beam tube connection of the module were chosen for venting. For these tests the venting air flow was monitored by an Air Flow Measurement Device with a 3 inch orifice for the first 4 test and through the 4 inch opening for the 5th test A fast acting vacuum valve was used for triggered venting. Only minor damages occurred after venting the insulating vacuum of the cryomodule with no measurable consequences for the performance. Their conclusion was the robust cryomodule design could be validated and “Hence, the consequences for the layout of the cryogenic systems, which were derived from the simulations, can be considered as safe”.


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Supply and return Pressure are same for MLC and XFEL

CONCLUSIONS

1)Oxygen deficiency hazard should not be a problem

2)Over pressurization of Helium Supply and return lines should be handle outside of MLC

3)Helium leaks into Vacuum vessel can be handed by appropriately sized Cryostat pressure relief valve

4)From XFEL test over pressurization of Vacuum vessel from air leaks to vacuum vessel or beam line should not cause a problem.


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references1) ERL DEIS appendix P2-117 /2-118

2) EXPERIMENTAL TESTS OF FAULT CONDITIONS DURING THE CRYOGENIC

OPERATION OF A XFEL PROTOTYPE CRYOMODULE

Boeckmann T., et : Deutsches Elektronen Synchrotron, 26607 Hamburg, Germany


safety requirements and regulations 10/3/20121safety requirements & regulations james sears

Documents

safety ehs

safety oversight

safety committees

inventory of helium

helium inventory

helium vessels

event helium

gallons of liquid helium