Year
2016
Abstract
Template-based analysis has emerged as a popular candidate method for treaty verification applications. This technique is useful in a wide range of digital image processing scenarios where speed and sensitivity are highly valuable. It is also conceivable to sequester the sensitive information likely to be contained in a template behind an information barrier. In this work we demonstrate the use of a template-based analysis using measured correlated signatures of fission born gammas and neutrons. In the past this signature has been shown to be useful in discriminating non-multiplying neutron sources (e.g. Cf-252, Am-Be) from Special Nuclear Material (SNM). Given sufficient numbers of correlated events it is possible to characterize the relative multiplication of SNM as well as the presence of any intervening shielding or moderating material. This signature is sensitive to small changes in multiplication, because the timing between correlated events is strongly dependent on the length of fission chains in the SNM. Using a template correlation method we demonstrate the application of this signature for dismantlement and item (warhead) confirmation. We characterized the sensitivity and specificity of this approach as a function of time using measurements of the well characterized Beryllium Reflected Plutonium (BeRP) ball and Training Assembly for Criticality Safety (TACS) which are nested hemispherical shells of highly enriched uranium (HEU). With an operational threshold yielding 99% True Positive (TP) rate we achieved a sub 1% False Positive (FP) rate in at most 12 and 590 seconds for the BeRP ball and HEU dismantlement, respectively. Item confirmation was tested for both objects against Cf-252 and low-multiplying WGPu Plutonium Oxide Hemispheres (Hemis). We were able to achieve similar dwell times for item confirmation tests required to achieve the same TP and FP operational thresholds.