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The sensitivity of the methods of analysis will be particularly important when the amount of evidence is small. In some cases, illicit traffickers may initially deliver only a tiny sample, which is purportedly representative of a much larger batch of material, to their customer. Even for interdictions of large amounts of material, the analytical techniques should be as sensitive as possible, because trace species are often significant components of a signature. However, as the sensitivity of the analysis increases, so does the susceptibility to contamination and other interferences. For example, the analyst might have to decide whether the Fe and Cr detected in the analysis is the signature of a certain manufacturing process or merely contamination from a stainless steel spatula used to collect the evidence.

Communication of Results

All results and assessments must be communicated in the form of a technical report. Reports may be issued periodically during and after the conclusion of an interdiction event to keep decision makers apprised of recent data and insights from the investigation. For example, the laboratory could issue reports to coincide with the availability of results from the sequence of techniques and methods in Table 1 (24 hours, one week, two months). However, a final report must also be issued after the conclusion of the event. The nuclear forensics laboratory should identify all data and other information used in the assessment and include the rationale for the conclusion. The laboratory should also identify any information that conflicts with the assessment and why they are choosing to disregard or discount that information.

Ideally, there should be an unambiguous method of specifying the confidence in the conclusions to decision-makers. The international nuclear forensics community has not yet reached a consensus on such a method. It is difficult to summarize a vast body of evidence, each with its own uncertainty, with a single categorization. However, such a categorization must be made to communicate the strength of the evidence to decision makers who might not have the requisite technical background to rigorously evaluate all stages of data acquisition and analysis. Therefore, nuclear forensic researchers are seeking to develop and demonstrate methods to articulate confidence in nuclear forensics interpretations that are based on combining disparate data and information. The articulation of confidence when formulating conclusions based on disparate datasets is at the heart of enabling credible interpretations of nuclear forensics data.

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