Security risk assessment of process plants: the role of layout

After the accident of Toulose and the terrorist attack of September 11, interest is growing about the security of process plants: recommendations [1], guidelines [2] and standards [3], have been issued and security risk assessment (SRA) approaches have been proposed in the literature [4-10]; other works assess the attractiveness and/or vulnerability of industrial targets [11-13]. Among the various factors affecting the security of a process plant, the layout of the plant may play a significant role, since the different parts of the installation may be more or less easily reached by a terrorist attack and present different potentials for causing a major accident, including the possibility of domino effects. The present work will focus on the influence of the layout of a process plant on its security and on its possible impact on the external environment: the different approaches will be critically examined to extract the essential information concerning this issue, in order to derive some general guidelines to support the choice of a layout contributing not only to the safety but also to the security of the installation. Study cases, relevant to some existing Italian installations, will be then examined to assess the efficacy of their layout from the security point of view.