J. Miller W. Charlton “Analytical Inverse Model for Post-Nuclear Event Attribution of Plutonium”, Annual Meeting of the Institute for Nuclear Materials Management, July 8-12, 2007, Tucson, AZ.
An integral part of deterring nuclear terrorism is the swift attribution of any event to a particular state or organization. By quickly being able to identify the responsible party after a nuclear event, we can ensure that the appropriate people are held accountable for their actions. Currently, there is a system in place to determine the origin of nuclear devices and materials from post-event data; however, the system requires time to produce an answer within acceptable error margins. Described here is a deterministic approach derived from first principles to solve the inverse problem. We start with the basic change rate equation, and derive relationships for important nuclear concentrations and device yield. This yields a very computationally efficient method for producing an estimate of the material attributes. This estimate can then be used as a starting point for other more detailed methods, thus reducing the overall computation time of the post-event forensics. This work focused on a specific type of nuclear event: a plutonium IND explosion. From post-event isotopic ratios, this method determines the device1″s pre-event isotopic concentrations of special nuclear material. From the original isotopic concentrations, we can narrow the field of the possible origins for the nuclear material. In this method, knowing where the nuclear material did not originate is as important as knowing where it did. We have seen results in an ideal case (consisting of 95% Pu-239 and 5% Pu-240) within a two percent margin of error.