Publications

Recent examples provide a significant concern for the resilience of the U.S. electric grid and represent a need for enhanced decision-making to address an increasingly wide range of complex system interactions and potential consequences. In response, this LDRD project produced a proof-of-concept evaluation called the Resilience and Hazard Assessment to Prioritize Security Operations for Decisions and Impacts (RHAPSODI) methodology as an agile and flexible analytic framework capable of addressing multiple, diverse threats to desired electric grid performance. After empirically grounding needs for the future of U.S. electric grid resilience, this project employed the systems-theoretic process analysis (STPA) to develop a systems engineering risk model. The results of a completed feasibility study of a notional high voltage transmission system demonstrate an improved ability to incorporate both spatial (e.g., geographically distributed) and temporal (e.g., dynamic and time-dependent) elements of security risk to the gird. The success of this LDRD project provides the foundation for further evolution of the systems engineering risk model for the grid; derivation of quantitative approaches to evaluate risk and resilience performance; facilitation of agile experimenting and grid sensitivity to a range of vulnerabilities; and development of tools to assist decision-makers in enhancing U.S. electrical grid resilience.

Researchers at Sandia National Laboratories, in conjunction with the Nuclear Energy Institute and Light Water Reactor Sustainability Programs, have conducted testing and analysis to reevaluate and redefine the minimum passible opening size through which a person can effectively pass and navigate. Physical testing with a representative population has been performed on both simple two-dimensional (rectangular and circular cross sections up to 91.4 cm in depth) and more complex three-dimensional (circular cross sections of longer lengths up to 9.1 m and changes in direction) opening configurations. The primary impact of this effort is to define the physical design in which an adversary could successfully pass through a potentially complex opening, as well as to define the designs in which an adversary would not be expected to successfully traverse a complex opening. These data can then be used to support risk-informed decision making.

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Vital Area Identification (VAI) is an important element in securing nuclear facilities, including the range of recently proposed advanced reactors (AR). As ARs continue to develop and progress to licensure status, it will be necessary to ensure that safety analysis methods are compatible with the new reactor designs. These reactors tout inherently passive safety systems that drastically reduce the number of active components whose failures need to be considered as basic events in a Level 1 probabilistic risk assessment (PRA). Instead, ARs rely on natural processes for their safety, which may be difficult to capture through the use of fault trees (FTs) and subsequently difficult to determine the effects of lost equipment when completing a traditional VAI analysis. Traditional VAI methodology incorporates FTs from Level 1 PRA as a substantial portion of the effort to identify candidate vital area sets. The outcome of VAI is a selected set of areas deemed vital which must be protected in order to prevent radiological sabotage. An alternative methodology is proposed to inform the VAI process and selection of vital areas: Systems-Theoretic Process Analysis (STPA). STPA is a systems-based, top-down approach which analyzes a system as a hierarchical control structure composed of components (both those that are controlled and their controllers) and controlled actions taken by/acted upon those components. The control structure is then analyzed based on several situational parameters, including a time component, to produce a list of scenarios which may lead to system losses. A case study is presented to demonstrate how STPA can be used to inform VAI for ARs.

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