The development of a set of safety codes and standards for hydrogen facilities is necessary to ensure they are designed and operated safely. To help ensure that a hydrogen facility meets an acceptable level of risk, code and standard development organizations are utilizing risk-informed concepts in developing hydrogen codes and standards.This report describes the application of a risk-informed process to establish one code requirement: the separation distances between a bulk gaseous hydrogen storage facility and the public at large. A risk-informed process, as opposed to a risk-based process, utilizes risk insights obtained from quantitative risk assessments (QRAs) combined with other considerations to establish code requirements. The QRAs are used to identify and quantify scenarios for the unintended release of hydrogen, identify the significant risk contributors at different types of hydrogen facilities, and to identify potential accident prevention and mitigation strategies to reduce the risk to acceptable levels. Other considerations used in this risk-informed process include the results of deterministic analyses of selected accidents scenarios, the frequency of leakage events at hydrogen facilities, and the use of safety margins to account for uncertainties.The risk-informed approach results in a defensible technical basis for specifying separation distances for hydrogen facilities. The results also demonstrate that separation distances for hydrogen facilities can be significantly affected by facility design parameters such as the system operating pressure and available mitigating features, component leakage frequency data, and the selected consequence measures and risk guidelines used in the evaluation. The separation distances generated in this report have been accepted for incorporation into revisions of several hydrogen facility standards.iv
The development of an infrastructure for the future hydrogen economy will require the simultaneous development of a set of codes and standards. As part of the U.S. Department of Energy Hydrogen, Fuel Cells & Infrastructure Technologies Program, Sandia National Laboratories is developing the technical basis for assessing the safety of hydrogen-based systems for use in the development/modification of relevant codes and standards. This work includes experimentation and modeling to understand the fluid mechanics and dispersion of hydrogen for different release scenarios, including investigations of hydrogen combustion and subsequent heat transfer from hydrogen flames. The resulting technical information is incorporated into engineering models that are used for assessment of different hydrogen release scenarios and for input into quantitative risk assessments (QRA) of hydrogen facilities. The QRAs are used to identify and quantify scenarios for the unintended release of hydrogen and to identify the significant risk contributors at di fferent types of hydrogen facilities. The results of the QRAs are one input into a risk-informed codes and standards development process that can also include other considerations by the code and standard developers. This paper describes an application of QRA methods to help establish one key code requirement: the minimum separation distances between a hydrogen refueling station and other facilities and the public at large. An example application of the risk-informed approach has been performed to illustrate its utility and to identify key parameters that can influence the resulting selection of separation distances. Important parameters that were identified include the selected consequence measures and risk criteria, facility operating parameters (e.g., pressure and volume), and the availability of mitigation features (e.g., automatic leak detection and isolation). The results also indicate the sensitivity of the results to key modeling assumptions and the component leakage rates used in the QRA models.
The permitting process for hydrogen fueling stations varies from country to country. However, a common step in the permitting process is the demonstration that the proposed fueling station meets certain safety requirements. Currently, many permitting authorities rely on compliance with wellknown codes and standards as a means to permit a facility. Current codes and standards for hydrogen facilities require certain safety features, specify equipment made of material suitable for hydrogen environment, and include separation or safety distances. Thus, compliance with the code and standard requirements is widely accepted as evidence of a safe design. However, to ensure that a hydrogen facility is indeed safe, the code and standard requirements should be identified using a risk-informed process that utilizes an acceptable level of risk. When compliance with one or more code or standard requirements is not possible, a n evaluation of the risk associated with the exemptions to the requirements should be understood and conveyed to the Authority Having Jurisdiction (AHJ). Establishment of a consistent risk assessment toolset and associated data is essential to performing these risk evaluations. This paper describes an approach for risk-informing the permitting process for hydrogen fueling stations that relies primarily on the establishment of risk-informed codes and standards. The proposed risk-informed process begins with the establishment of acceptable risk criteria associated with the operation of hydrogen fueling stations. Using accepted Quantitative Risk Assessment (QRA) techniques and the established risk criteria, the minimum code and standard requirements necessary to ensure the safe operation of hydrogen facilities can be identified. Riskinformed permitting processes exist in some countries and are being developed in others. To facilitate consistent risk-informed approaches, the participants in the International Energy Agency (IEA) Task 19 on hydrogen safety are working to identify acceptable risk criteria, QRA models, and supporting data 1 .
Sandia National Laboratories is developing the technical basis for assessing the risk of hydrogen infrastructure for use in the development of relevant codes and standards. The development of codes and standards is an important step in ensuring the safe design and operation of the hydrogen fuel cell infrastructure. Codes and standards organizations are increasingly using risk-informed processes to establish code requirements.Sandia has used Quantitative Risk Assessment (QRA) approaches to risk-inform safety codes and standards for hydrogen infrastructures. QRA has been applied successfully for decades in 3 many industries, including nuclear power, aviation, and offshore oil. However, the hydrogen industry is a relatively new application area for QRA, and several gaps must be filled before QRA can be widely applied to reduce conservatisms that influence the safety requirements for hydrogen installations.This report documents an early-stage QRA for a generic, code-compliant indoor hydrogen fueling facility. The goals of conducting this activity were threefold: to provide initial insights into the safety of such facilities; to recommend risk-informed changes to indoor fueling requirements in safety codes and standards; and to evaluate the quality of existing models and data available for use in hydrogen installation QRA. The report provides several recommendations for code changes that will improve indoor fueling safety. Furthermore, the report provides insight into gaps in the QRA process that must be addressed to provide greater confidence in the QRA results.4
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