The development of a set of safety codes and standards for hydrogen facilities is necessary to ensure that those facilities are designed and operated safely. To help ensure that a hydrogen facility meets an acceptable level of risk, the National Fire Protection Association (NFPA) is utilizing risk-informed concepts in developing the NFPA 2 model hydrogen code.
This paper describes the application of a risk-informed process to establish one code requirement: the separation distances between a hydrogen 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 resulted in a defensible technical basis for specifying the separation distances in the NFPA 2 model code. 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.