This thesis discusses the use of a model-based systems engineering (MBSE) approach for physical protection systems (PPS) evaluation. We discuss the role of requirements analysis in Vulnerability Assessment (VA). Then, we discuss different tools that are being used for requirement analysis and demonstrate how requirements modeling tools can be used in analyzing requirements for VA. Next, we review the steps in vulnerability assessment (VA) and describe the use of SysML models in these steps. The thesis presents examples of SysML models that can be used when conducting VA. Such models can enable the development and integration of other VA tools and reduce the time and cost of conducting VA, which will lead to safer facilities.