A Study on the Derivation of Safety Requirements for Hydrogen Systems in Railway Vehicles Based on Hazard Analysis

With the global push toward carbon neutrality, the development of hydrogen-fueled rail vehicles is actively progressing to replace aging diesel trains. While hydrogen trains offer zero-emission operation and long-range capabilities, they incorporate high-risk technologies such as high-pressure hydrogen storage systems, fuel cell power systems, and high-voltage batteries. Hydrogen exhibits extremely low ignition energy and high flammability. Combined with railway-specific operating environments—such as tunnels, underground sections, and continuous vibration—rigorous safety verification is essential for various accident scenarios, including storage tank ruptures, valve failures, overpressure during refueling, and battery thermal runaway. However, due to the lack of operational experience and accident data, applying conventional railway practices or safety standards from other industries presents clear limitations. Therefore, this study proposes a methodology for hazard analysis and safety requirements derivation tailored to hydrogen rail vehicles by integrating the railway RAMS standard (IEC 62278) risk management process with hydrogen-related international standards (ISO, IEC). Potential hazards were identified by conducting a Hazard and Operability (HAZOP) analysis based on system definition, operating modes, functional analysis, and relevant standards review. Mitigation measures were established for each identified hazard to derive finalized safety requirements. Furthermore, by establishing verification plans for the derived safety requirements, this study provides technical safety assessment criteria applicable to the demonstration and commercialization stages of hydrogen rail vehicles.