Nuclear forensics requires accurate identification of distinguishing characteristics and provenance of interdicted nuclear materials. It has been known that various production processes and interactions with changing environments can affect the morphology and associated chemistry of nuclear materials. In this presentation, we describe our multiplatform approach using high-resolution microscopic techniques to identify spatially resolved morphological and chemical features within the bulk plutonium (Pu) and uranium (U) materials. The approach involves electron microanalysis with scanning electron microscopy (SEM), focused ion-beam (FIB) tomography with SEM, three-dimensional (3D) spatial modeling, chemical analysis with Auger and X-ray photoemission spectroscopies. Our work shows that the three-dimensional (3D) characterization and spatial modeling of the interior of the bulk nuclear material provide higher-fidelity morphological features than conventional two-dimensional (2D) morphological characterization methods. Both Pu and U metals have microscopic inclusions distributed extensively with complex morphology. Inclusions from impurities such as carbon and iron reveal the production history tied to the chemical and metallurgical processes. Both Pu and U metals have morphological and chemical features entrapped within their bulk oxide scales that form from exposure to changes in atmospheres. These altered oxide scales provide distinguishing characteristics for recent provenance.
Prepared by LLNL under Contract DE-AC52-07NA27344. This work was supported by the Office of Defense Nuclear Nonproliferation Research and Development within the U.S. Department of Energy’s National Nuclear Security Administration. This work has been supported by the U.S. Department of Homeland Security (DHS), Domestic Nuclear Detection Office (DNDO), under a competitively awarded IAA No. HSHQDN-16-X-00044. This support does not constitute an express or implied endorsement on the part of the Government. LLNL-ABS-740142