Design of a Cargo Scanning Experiment to Measure Differential-Die Away of Uranium

Cargo scanning plays an essential role in the national security strategy of the Department of Homeland Security (DHS). The continuous improvement of radiation detection techniques is imperative to maintain a strong defense against contraband smuggling. The University of Tennessee (UT) has developed a cargo container active neutron interrogation system based on the differential die-away method to identify the presence of shielded nuclear material in various cargo configurations. In preparation for measurements at the Y-12 National Security Complex, our initial experimental setup uses 20 kg of natural uranium as simulated contraband targets within the cargo container. The container is then filled with hydrogenous materials to replicate cargo contents. A Sodern Genie 16 deuterium-tritium neutron generator is used to produce 14.1 MeV neutrons, which are moderated by a custom-designed moderator assembly. Stimulated neutrons are detected by fast neutron detectors, including a liquid scintillator, a stilbene scintillator, and an organic glass scintillator. This work describes the experimental setup, the measurement procedure, and the first experimental results.