Threat Characterization in Nonproliferation Assessment

NNSA established a nonproliferation assessment methodology (NPAM) working group in 2002 to survey and advance methodologies for performing quantitative, reproducible assessments of nonproliferation activities and programs. Because of the complexity of nonproliferation assessments, the problem must be decomposed into manageable elements. The proposed decomposition involves the definition of a finite set of threats, identification of proliferation resistance measures, and development of metrics to evaluate the effectiveness of these measures against the threats. This paper concentrates on one component of the NPAM effort. It discusses the characterization of proliferation threats and their implications in performing nonproliferation assessments. The spectrum of potential threats of nuclear proliferation is complex and ranges from small terrorist cells to industrialized countries with advanced nuclear fuel cycles. Adding to this complexity, the potential objectives of these threats may be highly multidimensional. Three categories of potential proliferant organizations discussed are sub-national organizations, developing states, and developed states. These three categories can be further subdivided depending on the aspirations of the proliferant regarding number of weapons sought, weapon yield, weapon reliability, and delivery vehicle. Because a fuel cycle’s proliferation resistance depends on the specific threat being evaluated, some assessments may be a vector of results with a calculated value of proliferation resistance for each threat. The alternative would be an aggregation of results where the proliferation resistance is averaged over the different threats, but valuable information may be lost in integrating results this way. The guidelines document describes the metrics that can be used to assess proliferation risk or proliferation resistance. Although a hierarchy of metrics can be developed, the definition and measurement of metrics vary depending on the character of the threat and the analysis approach. Proliferation barriers protecting against a sub-national terrorist organization differ from those that might be effective against a developed state. While passive proliferation resistance barriers may be useful, they will not likely be effective against all classes of threats. Thus, integrated proliferation resistance will require a combination of strong passive as well as active measures in order to optimize effectiveness. Additional development work is required to fully understand proliferation metrics, their associated measures, and their weights for the different types of threat, and meaningful approaches to aggregate the effectiveness of layered barriers.