1. Safety Requirements and Regulations 10/3/20121Safety Requirements & Regulations James Sears

2. Safety Requirements and Regulations Responsibility for safety oversight is carried out by safety committees within CLASSE and by Cornell’s Department of Environmental Health and Safety (EH&S). 10/3/20122Safety Requirements & Regulations James Sears

3. Safety Requirements and Regulations CLASSE has over four decades of experience designing, building and collaborating on SRF and Cryogenic systems 10/3/20123Safety Requirements & Regulations James Sears

4. Cryostat Safety Issues Personal safety & Equipment protection 10/3/20124Safety Requirements & Regulations James Sears

5. Cryostat safety issues Oxygen deficiency hazard Over pressurization 10/3/20125Safety Requirements & Regulations James Sears

6. Oxygen deficiency hazards No 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 6

7. Oxygen deficiency hazards Liquid 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 10/3/2012 Safety Requirements & Regulations James Sears 7

8. 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 10/3/2012 Safety Requirements & Regulations James Sears 8

9. Over Pressurization 10/3/2012 Safety Requirements & Regulations James Sears 9 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

10. 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 operations 2 so lets look at will look at their test for a) Helium supply leak b) Accidental loss of insulation or cavity vacuum 10/3/2012 Safety Requirements & Regulations James Sears 10

11. XFEL test For 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 5 th 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”. 10/3/2012 Safety Requirements & Regulations James Sears 11

12. 10/3/201212Safety Requirements & Regulations James Sears Supply and return Pressure are same for MLC and XFEL

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16. 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. 10/3/2012 Safety Requirements & Regulations James Sears 16

17. references 1) 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 10/3/201217Safety Requirements & Regulations James Sears