Risk Reduction Evaluation of Prescriptive Technical Codes for Hydrogen Refueling Stations Using LOPA

This study evaluates the risk reduction performance of prescriptive technical codes applied to hydrogen refueling stations using a Layer of Protection Analysis (LOPA) approach. A representative accident scenario involving high-pressure hose rupture at the dispenser was selected as the initiating event, and the initiating event frequency was determined based on CCPS guidelines. The target mitigated event likelihood (TMEL) was set to 1.0×10−6/year, resulting in a required risk reduction factor (RRF) of 1.0×104. Safety devices specified in the Korean Gas Safety (KGS) Codes were identified as independent protection layers (IPLs), and their probability of failure on demand (PFD) values were assigned based on commonly accepted LOPA data. The combined PFD of the identified IPLs was estimated to be 1.0×10−5, leading to a mitigated event likelihood of 1.0×10−7/year, which satisfies the predefined TMEL. These results indicate that the prescriptive technical codes can provide a certain level of quantitative risk reduction when all required safeguards operate as assumed. However, the analysis also reveals structural limitations associated with independence assumptions, potential common cause failures, and maintenance conditions. The findings suggest that integrating functional safety concepts and systematic risk assessment with prescriptive codes could enhance the reliability of safety management for hydrogen refueling stations.