Attributes and Thresholds in Measurements for Transparency Initiatives

The collection of programs broadly termed “Transparency Initiatives” frequently involves physics measurements that are applied to items with sensitive or classified properties. The inability or reluctance to perform quantitative measurements, in the safeguards tradition, to such items, and then to expose the results to international examination, has impelled development of an “attributes” approach to measurements, following the philosophy “if it looks like a duck, walks like a duck and quacks like a duck, call it a duck.” This approach avoids certain of the classification issues that would otherwise be associated with such measurements. Use of the attributes approach, however, continues to pose problems of interpretation, in light of the need to establish numerical thresholds whereby data obtained from the measurements can be evaluated to determine whether the attribute is present. In this paper we examine the foundations of the attributes approach and the steps used to determine appropriate attributes and thresholds, using examples from contemporary threat-reduction initiatives where possible. Implications for the detector technologies used in the measurements will be discussed, as will the characteristics of so-called “information barriers” intended to prevent inadvertent release of sensitive information during attributes measurements.