Development of a Comprehensive Framework for the Assessment of Technological Scenarios Triggered by Natural Events (Natech) in the Chemical and Process Industries

The interaction between natural hazards and chemical and process installations might lead to severe technological scenarios involving hazardous materials. These events are termed as Natech accidents and have several peculiarities that fall beyond the features of industrial accidents caused by internal factors. Indeed, natural events can simultaneously trigger multiple technological scenarios, leading to complex situations hard to be managed by emergency teams. Moreover, natural hazards can affect utilities and lifelines required to guarantee the correct operation of processes and of the implemented safety measures. This impairment can produce peculiar scenarios if specific classes of substances are handled, and can influence the possibility of accident escalation and domino effect, eventually leading to complex cascading events. This thesis is aimed at developing the tools for a more comprehensive quantification of the Natech risk, with a specific focus on the possibility that utilities and safety barriers might be impacted during the accident. A novel paradigm is presented for the description of the dynamics of Natech events, to highlight the central role of utilities and safety barriers in accident chain progression. Subsequently, a complete approach to assess the modification of barrier performance during natural hazards is described and embedded in an approach to assess the modification of Natech escalation likelihood. Then, a set of quantitative risk assessment methodologies is presented, enabling the evaluation of Natech risk including the possibility of barrier depletion and accident escalation also via domino effects. The tools presented in this thesis will hopefully enhance the comprehension of complex Natech events and foster the development of effective strategies for risk reduction and management, pivotal issues to be addressed to improve the resilience of chemical and process sites to natural hazards also in the light of the possibility that their severity will be inflated by the effects of climate change.