Sandia National Laboratories Risk-Informed Separation Distances for Hydrogen Fueling Stations Jeffrey LaChance Sandia National Laboratories 11/19/2018 Preliminary Data

Outline Project Background Separation Distances Risk-Informed Approach Description Application to an Example Facility Input Data and Assumptions for QRA Models Preliminary Results Conclusions Future Work 11/19/2018 Preliminary Data

Project Background Work performed under U.S. DOE Hydrogen, Fuel Cells & Infrastructure Technologies Program, Multi-Year Research, Development and Demonstration Plan Hydrogen Safety, Codes & Standard R&D Sandia National Laboratories is developing the scientific basis for assessing credible safety scenarios and providing the technical data for use in the development of codes and standards Includes experimentation and modeling to understand behavior of hydrogen for different release scenarios Use of Quantitative Risk Assessment (QRA) methods to help establish separation (setback, safety) distances at hydrogen facilities and to identify accident prevention and mitigation strategies for key risk drivers 11/19/2018 Preliminary Data

Separation Distances Specified distances in codes separating H2 components from the public, structures, flammable material, and ignition sources Distance vary with possible consequences from hydrogen releases (e.g., radiation heat fluxes or overpressures) Distances influenced by facility design parameters (e.g., hydrogen pressure and volume), available safety features (e.g., isolation valves), and release parameters (e.g., leak size and location) Separation distances based solely on the consequences of hydrogen leaks can be large! 11/19/2018 Preliminary Data

Example of Consequence-Based Separation Distances for a Jet Fire Leak Diameter(mm) 11/19/2018 Preliminary Data

Separation Distances for Different Consequence Measures 11/19/2018 Preliminary Data

Risk-Informed Approach Uses risk insights plus other considerations to help define code requirements Risk = Frequency X Consequence from all accidents Requires hydrogen component leak frequencies Requires definition of important consequences Uses QRA and consequence models to evaluate risk Requires definition of acceptable risk levels Accounts for parameter and modeling uncertainty present in analysis 11/19/2018 Preliminary Data

Risk Approach for Establishing Separation Distances Cumulative frequency of accidents requiring this separation distance Cumulative frequency of accidents requiring this separation distance 11/19/2018 Preliminary Data

Use of Risk Eliminates Large Leaks from Consideration Pipe Leak Frequency Increasing Leak Diameter 11/19/2018 Preliminary Data

Application to Example Facility Currently evaluating risk-informed separation distances for a representative fueling facility To demonstrate risk methodology To evaluate important facility features (e.g., gas volume and leak isolation features) To determine importance of modeling parameters (e.g., data, geometry, temporal effects) To identify key risk scenarios and identify possible ways to reduce the risk to acceptable levels Work presented is focused on hydrogen jet releases from gas pipes and gas storage cylinders 11/19/2018 Preliminary Data

Example Facility Description Facility can refuel 100 cars/day All components located outside Liquid hydrogen facility with no-onsite production Liquid storage volume of 3000 kg @ 0.55 Mpa Cryo pump (11 L/min) used to provide pressurized liquid to vaporizer when pressure in gas storage decreases Natural draft vaporizer Gas storage was sized for 500 kg of hydrogen(12.63 m3 for 10000 psig facility) Three separate cascades Two refueling dispensers Facility meets codes and standards 11/19/2018 Preliminary Data

Leakage Frequency Distributions 11/19/2018 Preliminary Data

Consequence Parameters and Risk Criteria Used in Current Analysis Radiant Heat Flux from Jet Fires: 1.6 kW/m2 – no harm to individuals for long exposures 4.7 kW/m2 – injury (second degree burns) within 20 seconds 25 kW/m2 – 100% lethality within 1 minute; equipment and structural damage Hydrogen Concentration from Un-ignited Releases: 4%, 6%, and 8% concentrations – lower flammability limit Risk Criteria Frequency of Fatality to Individual at Separation Distance Used as Upper Bound Accident Frequency Criteria <2E-4/yr – fatality risk from all other high-risk hazards in society 11/19/2018 Preliminary Data

Gas Pipe Analysis Assumptions Leakage can occur in 50 m of 13.5 mm diameter pipe, 4 valves, 2 instrument lines (4.23 mm D), and 3 flanges Hydrogen leak or flame detector sends signal to isolation valve resulting in closure within 10s Immediate ignition results in fatality at separation distance if not automatically detected and isolated (no credit for manual detection and isolation) Delayed ignition of un-isolated gas jet results in flash fire Fatality assumed out to distance corresponding to LFL (used to determine separation distance) Pipe leak orientation was assumed directed at lot line resulting in maximum separation distances 11/19/2018 Preliminary Data

Gas Pipe Leak Event Tree D-IGNITION Delayed Ignition of Hydrogen ISOLATION Automatic Isolation of Pipe within 10s DETECTION Detection of Hydrogen or Flame I-IGNITION Immediate Ignition of Hydrogen Jet PIPE_LEAK Pipe Leak or Rupture Downstream of # END-STATE-NAMES 1 JET-FIRE-(10-S) 2 JET-FIRE 3 4 GAS-RELEASE-(10-S) 5 FLASH-FIRE 6 GAS-RELEASE 7 8 pipe leak - (New Event Tree) 2007/01/27 Page 0 11/19/2018 Preliminary Data

Gas Pipe Results: Un-isolated Jet Fires Mean frequency of any size un-isolated pipe leak < 1E-6/yr 11/19/2018 Preliminary Data

Gas Pipe Results: Isolated Jet fire Exposure time to isolated jet fires is short which reduces potential for structural or equipment damage and personnel injury. 11/19/2018 Preliminary Data

Frequency of Fatality from Isolated Jet Fire (10 s exposure) 10 s exposure to 25 kw/m2 heat flux results in 20% probability of a fatality (reducing the exposure time to 5 s would further reduce the probability to 5%). Operating Pressure 11/19/2018 Preliminary Data

Gas Pipe Results: Flash Fires Delayed ignition assumed to result in flash fire and fatality out to LFL. Hydrogen Concentration 11/19/2018 Preliminary Data

Gas Storage Analysis Assumptions For each storage cylinder, leakage can occur in 1 m of 4.23 mm diameter pipe and 1 valve attached to the cylinder, and from the cylinder itself. Leakage can also occur in manifold and 4 attached valves. No protective barriers are installed around the gas storage area No isolation of a gas storage leak from these components is possible Gas storage is outdoors and thus there is little potential for a hydrogen detonation Immediate ignition results in fatality at separation distance if not automatically detected and isolated (no credit for manual detection and isolation) Delayed ignition of un-isolated gas jet results in flash fire Fatality assumed out to distance corresponding to LFL (used to determine separation distance) Leak orientation was assumed to result in worst consequences (sensitivity study performed) 11/19/2018 Preliminary Data

Gas Storage Leak Event Tree 11/19/2018 Preliminary Data

Gas Storage Results: Un-isolated Jet Fires Risk-informed separation distances are affected by leakage contribution from different components. Leakage from all components Manifold and cylinder leaks Heat Flux Cylinder leaks 11/19/2018 Preliminary Data

Gas Storage Results: Flash Fires Flash fires, not jet fires, require the longest separation distances (36 m for an LFL of 4% vs.18 m for 25 kw/m2 heat flux - 2E-4/yr fatality criteria). Hydrogen Concentration 11/19/2018 Preliminary Data

Gas Storage Sensitivity Study – Volume of Stored Gas Limiting gas storage volume can lead to reduced risk-informed separation distances. Mass of Gaseous Hydrogen 11/19/2018 Preliminary Data

Gas Storage Sensitivity Study – Size of Gas Cylinders Increasing the gas cylinder size reduces the leakage frequency. Cylinder Size 11/19/2018 Preliminary Data

Example Separation Distances: Lot Lines Maximum Risk-Informed Separation Distances (m) Pipe Leaks1 Gas Storage Leaks2 Criteria 5000 psig 10000 psig 15000 psig 2E-4/yr 13-26 16-32 19-36 5E-5/yr 17-30 22-44 24-49 1E-5/yr 9 13 15 29-59 38-76 44-87 5E-6/yr 12 17 20 40-72 40-82 46-92 Pipe separation distances are limited by isolated jet fires (25 Kw/m2). Gas storage separation distances are limited by flash fires (8% - 4% H2 concentration). 11/19/2018 Preliminary Data

Conclusions from Example Pipe Analysis Properly designed and installed hydrogen and flame detection and automatic isolation capability can reduce the risk from piping leaks Frequency of un-isolated jet fire and flash fire scenarios can be small enough to justify short risk-informed separation distances. Separation distances are limited by isolated jet fire scenarios. Isolation capability at dispensers, vaporizers, and a facility with a compressor will likely result in similar results as above. 11/19/2018 Preliminary Data

Conclusions from Example Gas Storage Analysis Gas storage leakage events are likely the dominant risk contributors for the example facility (accidents involving liquid hydrogen have not yet been evaluated) Relatively short risk-informed separation distances (<20 m) could be justified for jet fires for a fatality risk criteria >1E-5/yr. However, risk-informed separation distances are limited by flash fire scenarios (separation distances for high pressure facilities >40 m for a fatality risk criteria <1E-5/yr). Reducing the gas storage volume or using larger volume cylinders can reduce the frequency of gas leaks and resulting risk-informed separation distances. Risk-informed separation distances may still be too long for gas storage releases. Barriers surrounding the storage area may be required to reduce the risk to acceptable levels. 11/19/2018 Preliminary Data

Future Efforts Continue evaluating safety distances for example facility Liquid hydrogen storage leaks/ruptures Evaluate alternate methods for pressurizing gas (cryo pump vs. compressor) Dispensers Evaluate facilities using different methods for onsite hydrogen production (gas reforming and electrolysis) Improve methodology including consideration of time-dependent impacts, geometry factors, and incorporation of uncertainty Get consensus on failure data for use in QRA (e.g., leak frequencies and component failure rates) Identify range of models or data for accident phenomenology probabilities (e.g., ignition and detection probabilities) Identify key risk drivers for hydrogen facilities and identify what can be done to reduce the risk and separation distances to acceptable levels Extend evaluation to other types of hydrogen facilities 11/19/2018 Preliminary Data