Quantitative performance assessment of physical security barriers for chemical facilities

Malicious acts of interference and terroristic attacks may affect chemical facilities causing severe accidents, with potential catastrophic consequences for people, environment and asset. The lack of a consolidated practice in the risk-informed implementation of security countermeasures goes hand in hand with the existence of very few rigorous approaches to the effectiveness assessment of security systems, and in particular of Physical Protection Systems (PPS). The present study addresses the issue of quantitatively assessing the effectiveness of PPS adopted to protect chemical facilities, recognized as high-consequence loss physical assets. An extended set of quantitative expert judgment based data that take into account performance variations due to operative conditions was derived. The application of the results to the quantitative assessment of the contribution of security controls in reducing vulnerability was also addressed.