QRA considering multi-vessel failure scenarios due to a natural disaster - Lessons from Fukushima

The Fukushima accident is the largest nuclear power plant accident caused by a natural disaster, which shut off the cooling system. In this accident, natural disaster was an initiating event and caused a problem to a single unit, but then propagated to other units at the site. Since that accident, the nuclear industry in South Korea is now more concerned with multi-unit Probabilistic Safety Assessment (PSA) and is attempting to develop a new methodology since there are generally more than four units on one site in the country. Likewise, chemical industry would be vulnerable for a natural disaster with a domino effect since their combinations have not been adequately addressed in the history. The chemical and petrochemical industries have experienced a number of incidents/accidents related to multi-units such as vessels and tanks because many of these units are usually installed on a site. The chemical industry has a wide range of experience, but most scenarios have involved domino effects, while the study of multi-vessel accidents caused by natural disasters (i.e., earthquakes) is lacking. The purpose of this paper is to review past experiences in the chemical industry and adapt appropriate process safety applications using risk analysis related to multiple vessels (tanks) at a site. Several Quantitative Risk Analysis (QRA) approaches have been searched and employed to compare the risks of some chemical plant complexes in South Korea regarding multi-vessel (unit) failure scenarios due to natural disasters.