Definition of a NaTech risk analysis methodology for assessing tornado-related risk for storage tanks

Natural catastrophic events, such as storms, earthquakes, flooding, and lightning; impacting industrial activities can trigger accidental scenarios, causing the release of hazardous substances from installations and storage, in events referred to as “Na-Tech†(Natural and Technological). Most of the attention in the literature has been devoted to accidents triggered by floods and earthquakes, while no specific analysis protocols aimed at determining the risk posed by tornadoes and strong gusts of wind on industrial facilities are available. Consequently, the purpose of this paper is to fill a gap in NaTech risk assessment, developing a qualitative methodology for the initial assessment of tornado-related Na-Tech risk for storage tanks, as previous works based on historical analysis have identified storages as the most critical asset, serving as a screening tool to determine which situations require a much more expensive Quantitative Risk Analysis (QRA). In the proposed methodology suitable Key Hazard Indicators (KHIs) were defined, requiring a limited amount of resources and information both on the intensity and frequency of the stormy event and on the plant and the characteristics of the assets in it, organizing them using the Analytical Hierarchy Process as a multi-criteria decision tool. In so doing, a specific Na-Tech risk level can be associated with a given situation (i.e., a process plant located in a given territory). The developed methodology was applied to a case study plant, and then a sensitivity analysis to both the locations and parameters was performed.