ORNL is managed by UT-Battelle for the US Department of Energy Considerations for Engineering (and other) Controls for Oxygen Deficiency Safety Kelly Mahoney SNS Protection Systems Team Leader 2 Considerations for ODH Engineering Controls Catastrophic Leak? Helium truck venting after accident. Houston TX, USA 12 October, 2015 3 Considerations for ODH Engineering Controls US Research Facilities with Significant Superconducting Accelerator Technology Includes planned upgrades Facility for Rare Isotope Beams 4 Considerations for ODH Engineering Controls Oxygen Deficiency is a Significant Hazard at Accelerator Facilities Oxygen Deficiency is considered a significant hazard at most accelerator facilities due to the large volume of gas released in an accident. Near Infinite Supply High release rate can overwhelm civil design features Or Low release rate over a very long time can intert very large spaces 5 Considerations for ODH Engineering Controls Outcomes of ODH Injuries are Counter to Other Industrial Hazards US Labor Dept. data indicates there are more deaths from oxygen deficiency than injuries. Multiple Deaths Deaths Injury Near Miss Multiple Deaths Deaths Injury Near Miss Outcomes of Industrial Injuries Outcomes of Oxygen Deficiency Injuries Note: This graphic is for illustrative purposes only. It is not a data plot. 6 Considerations for ODH Engineering Controls Labs May Use their Cryogen Inventory in Multiple Areas Accelerators and Beam Transport Beam Transport Magnets Superconducting RF (SRF) Vacuum backfill High Voltage Insulator Targets and Experiments Cryo Targets Moderators Analyzing Magnets Detectors Fabrication and Test Facilities SC Component test facilities Clean rooms User and Staff Laboratories A facility with a large cryogen inventory will tend to distribute this resource to multiple users. There is an implicit expectation that support and mitigations will be consistent across the facility. 7 Considerations for ODH Engineering Controls SNS Superconducting Linac RHIC Superconducting Dipoles SNS Cryogenic Moderator JLab SHMS Detector 8 Considerations for ODH Engineering Controls What are Hazards Present During a Spill? Oxygen Deficiency Cold Burns Low Visibility Liquefaction of O 2 Temperature effects on infrastructure JLab helium spill test 9 Considerations for ODH Engineering Controls Hazard Controls Hierarchy Eliminate the Hazard Engineering - methods of controlling exposure to hazards by design of the process or work configuration Administrative controls which depend upon human awareness and compliance for their effectiveness Personal Protective Equipment (least effective) 10 Considerations for ODH Engineering Controls US DOE Guidance A Include ODH analysis for all work spaces with cryogens Implement controls consistent with the results of the hazard analysis (graded approach) Design of Entry/Exits should account for potential Oxygen Deficiency conditions Use layered controls Engineering Administrative PPE Use standardized posting and alarms site-wide 11 Considerations for ODH Engineering Controls Include anticipated types of work over the life of the facility Evaluate any space where people may work not just at tunnel floor level. Platforms Vertical bends Work requiring ceiling or subfloor access (crane access, changing light bulbs, HVAC work,) Include areas with limited egress in the evaluation of ability to flee an ODH area E.g. person on back side of beam line needs to exit due to ODH alarm egress path includes path to aisle way + distance to emergency exit 12 Considerations for ODH Engineering Controls Typical DOE Lab Approach Define and Classify Areas as ODH Areas Normally based on risk of fatality Risk based on probability of a release and potential for fatality Implement standard administrative and engineered controls based on area classification SLAC Controls JLab Controls 13 Considerations for ODH Engineering Controls #1 - Eliminate the Hazard Design robust controls and interlocks define process deviations and recovery quench detection and mitigation Route relief valve exhaust outside the beam enclosure Use flow restricting orifices to limit maximum flow rate to < evacuation rate (or air changes) where possible Block gas flow paths to uncontrolled areas Limit inventory available to small enclosures 14 Considerations for ODH Engineering Controls 15 Considerations for ODH Engineering Controls ODH Monitoring and Alarms Types of oxygen monitors Electro-Chemical Cell Diffusion Barrier Capillary Laser Paramagnetic Ultrasonic Zirconium oxide 16 Considerations for ODH Engineering Controls SIL of an Oxygen Deficiency Alarm System A SIL (performance level of an engineered safety function) is only applicable to the engineering controls. Does not take human response into consideration Turn on Exhaust Fans when O 2 level is 18% Other functions, e.g. turn on audible/visual alarms when O 2 level is 19.5%, still should have performance requirements. 17 Considerations for ODH Engineering Controls ODH Exhaust Systems Implementation among labs is mixed JLab: Passive vents at each end of the Linacs Not tied to smoke removal system SNS: Redundant Active exhausts in center of SC Linac Shared with smoke removal system Fresh air makeup air vents controlled by tunnel access state (PSS) 18 Considerations for ODH Engineering Controls ODH Alarms At least two levels Alert on minor deviation e.g. 19.5% Alarm on major deviation e.g. 18% Both notify accelerator and cryogenic operations Should have procedures for response Evacuation tone Visible ODH alarm beacons In cryo areas (Evacuate) Outside entries (Do not Enter) 19 Considerations for ODH Engineering Controls Other considerations - Engineering Monitor Coverage should be redundant to allow for one or more sensors sensor to be off-line. Pre-determine the minimum number of on-line monitors that provide safety function Account for number of sensors to activate evacuation alarms The efficiency of a fan in a He-air mix is not the same as air alone. Calculate the evacuation rate (Q) based on the molecular composition of the gases. Ice formed around relief valves during a release may hold the valve open until the supply is cut off or exhausted. Evaluate where a relief valve or burst disc is pointing. Can people or important equipment be in the plume? Is there a keep out zone? 20 Considerations for ODH Engineering Controls Other Considerations Misc. ODH Controls may be at odds with radiological and fire safety controls Seal off and contain or ventilate? Order of precedence of fire vs. ODH actions Sample draw systems may bring activated air to uncontrolled spaces Should have procedures and training for: when fixed ODH monitoring is off-line entry to an area to investigate an alarm or bad sensor use of portable alarms and escape PPE 21 Considerations for ODH Engineering Controls Summary A facility will use cryogens for multiple purposes. The facility should have a consistent set of policies and procedures for safety The best control is to eliminate the hazard by design. Engineering controls are the next best option. There are several technologies available for ODH monitoring and alarm functions. Choices made at this point, e.g. redundancy, can have a significant impact on facility operations.