An innovative framework for chemical and process facilities to support a comprehensive Natech risk assessment

The interaction between natural hazards and technological installations handling hazardous materials can produce complex cascading accidents termed as Natech events. Climate change and increasing vulnerability of industrial facilities caused a growing concern towards Natech hazards in recent years. Current methodologies addressing the identification and quantification of Natech scenarios mostly consider only the possibility of direct damage of process and storage equipment caused by natural hazards as earthquakes and floods. Nevertheless, recent severe Natech events as the Arkema accident (2017) demonstrated that the direct failure of equipment is not the sole possible accident trigger. Indeed, in these events the accident sequence was initiated by the impairment of auxiliary systems and utilities induced by the natural event. The present contribution proposes an innovative comprehensive framework to the identification of Natech scenarios and to the quantitative assessment of Natech risk. The new framework presented addresses the identification of both direct and indirect Natech scenarios and considers the possible failure of utilities in the evolution of the accident chain and in the escalation of accident consequences. Specific strategies for the identification of alternative routes leading to Natech events are suggested, considering loss of containment events caused either by the direct damage of equipment or by the failure of utilities or safety barriers. A test-case was defined to show the application of the framework. The results demonstrated the importance of the indirect route in determining the overall hazard due to Natech events when specific categories of hazardous substances are present on the site.