Awareness and mitigation of NaTech accidents: towards a methodology for risk assessment

Natural hazards affecting chemical and process facilities deserve particular attention since they can cause the release of hazardous substances possibly resulting in severe environmental pollution, explosions and/or fires (so-called NaTech accidents). Awareness of the hazard posed by Natech events is growing, and a need for explicitly including NaTech accidents into chemical-accident prevention and mitigation is nowadays widely recognized. Nevertheless, several elements that characterize Natech events still need to be investigated. In particular, only scarce data exists on equipment damage modes, release intensities and the final consequences for these accidents. The present contribution focuses on the development of a general framework for the assessment of NaTech risk. The analysis of past accident data allowed the gathering of data on the expected damage of process equipment caused by the impact of flood, lightning and earthquake events. Failure modes and damage states caused by these different natural events were identified. The expected intensity value of loss of containment (LOC) was obtained by statistical analysis.