NaTech scenarios caused by flooding: Evaluation of accident frequency by the use of fragility models

Natural events impacting on process plants may lead to severe technological accidents. These events are usually defined as NaTech events (Natural Hazard Triggering Technological Disasters). In order to derive the frequencies of accident scenarios associated to NaTech events for QRA (Quantitative Risk Assessment) implementation, a critical issue is the availability of equipment vulnerability models. The aim of the present study was to present a vulnerability model for the assessment of failure probability of atmospheric vessels involved in flooding events. The vulnerability model was based both on the severity of the natural event and on the construction features of the equipment. In order to explore the model features and its potentialities, the application to case-studies was carried out analysing an actual industrial layout. The results obtained confirmed that NaTech scenarios caused by floods may have an important influence on risk assessment and management of industrial facilities.