Using Vital Area Identification Insights In Security Effectiveness Evaluation

Security effectiveness evaluation of complex nuclear facilities, such as commercial nuclear power reactors, is especially challenging because of the large number and complex interactions of process and safety systems make it difficult to comprehensively identify the combinations of equipment that, if damaged, could create high radiological consequences (i.e., equipment targets). The vital area identification methodology, described in International Atomic Energy Agency (IAEA) Nuclear Security Series 16 (NSS-16), Identification of Vital Areas at Nuclear Facilities, leverages plant probabilistic safety assessment insights and models to comprehensively identify the combinations of areas from which the design basis threat could create high radiological consequences. These combinations of areas are referred to as target sets. However, the area focus of the NSS-16 approach obscures the specific equipment targets within the target set areas. This paper presents a systematic method to recover the equipment target information from the vital area identification sabotage logic model and plant layout. The method identifies all the equipment target combinations for initiating events of malicious origin (IEMOs) and mitigating systems disablement events in the logic model. The paper also presents a simple “bookkeeping” approach to manage effectively the very large number of combinations of equipment targets (typically in the tens of thousands to hundreds of thousands for a Generation 3 nuclear power reactor plant). This method also presents a systematic approach to highlight those combinations of equipment targets most vulnerable to the design basis threat based upon subjective or other criteria. This permits security analysts to focus on the most significant target sets and assign realistic task times and resource requirements for attacks on equipment within each of the target sets. These realistic task times and resource requirements can be used with qualitative or quantitative evaluation methods, such as computer path evaluation models. The approach presented can also be used to develop realistic sabotage scenarios for security response exercises that can be conducted as a part of security effectiveness evaluation.