From Incident Reports to Standardized Case Cards: A Lightweight Ontology and Knowledge Graph for Green Hydrogen Production Hazard Analysis

Incident reports provide valuable empirical evidence on hydrogen safety, yet their narrative structure limits reuse in engineering analysis. This study proposes a kernel-based framework that transforms incident data into standardized case cards that represent key physical-hazard processes. Five interconnected kernels are defined to capture hydrogen release, accumulation, dispersion, or explosion, mitigation through venting, and human exposure. A lightweight ontology links parameters, mitigation actions, and outcomes, while a knowledge graph enables structured storage and traceable retrieval. Application to publicly available incident data demonstrates improved comparability and analytical usability. The results suggest that kernel-based structuring provides a practical pathway for integrating empirical safety knowledge into engineering design and digital safety tools and may support future standardization of incident-based risk analysis.