Shipping Anomaly from NMIS Imaging

In 2007, a shipping container that arrived at ORNL was imaged using the neutron and gamma-ray imaging capability of the Nuclear Materials Identification System (NMIS). NMIS with imaging uses a time-tagged radiation source, which can be either a D-T neutron generator or a 252Cf spontaneous fission source. The initial imaging measurements used the D-T generator’s 14.1 MeV neutrons. Because of the low attenuation of the container and its contents, subsequent measurements were performed with the fission energy spectrum neutrons and gamma rays of the 252Cf source. The 252Cf source provides a simultaneous measurement of both a neutron (more sensitive to organics) and a gamma-ray (more sensitive to steels) image to be obtained. The images showed that the container contents were partially inverted instead of their expected arrangement. This information was useful in assessing the shipment packaging before the container was opened and indicates how NMIS with imaging can be used to image receipts.