TOWARD A NEW APPROACH FOR VITAL AREA IDENTIFICATION FOR CUTTINGEDGE NUCLEAR FACILITI

Current best practices in vital area identification (VAI) focus on preventing radiological sabotage in terms of damage to reactor cores and spent fuel during a range of distinct operational states. Given that radiological sabotage results in the same types of undesirable radiological releases as a nuclear accident, there is a significant amount of hazard and risk analysis that these VAI approaches leverage from regularly completed safety assessments. More specifically, these approaches translate event-tree and fault-tree models into potential sabotage logic models that identify various areas within a facility that those potential sabotage actions might occur. Yet, several trends in commercial nuclear facilities—such as increased digitization; non-traditional fuel cycles. including novel chemical and physical fuel forms; passive or inherent safety elements, and novel in-plant activities—are challenging the efficacy of such approaches. Particularly when considering new issues faced in achieving design certification for “advanced” or “modular” types of reactor designs, new approaches to VAI should be explored. In response, Sandia National Laboratories is investigating the efficacy of new analytical approaches to better meet today’s VAI needs. One new approach seeks to leverage “Master Logic Diagram (MLD)” models—a top-down logical structure designed to determine required facility functions—to help coordinate security-related insights from across data sources to support VAI. Similarly, systems theoretic process analysis (STPA)—a hazards analysis technique based on systems and controltheory—has attractive analytic characteristics to enhance VAI. Building on the structure of traditional VAI, the new approach captures more comprehensive (and non-linear) relationships between structures, systems. and components—supporting more efficient and effective VAIrelated design decisions. After briefly summarizing the traditional approach to VAI and highlighting areas of improvement, this paper will introduce several new analytic concepts poised to address this improvement area. Next, this paper will describe how these concepts can form a new VAI approach and will demonstrate its effectiveness with several anecdotes. Lastly, this paper will discuss conclusions, insights, and implications of the proposed VAI approach to support design and deployment decisions for nuclear facility security solutions.