Analysis of Manifests for Containerized Commodities Imported through US Ports

Special nuclear material (SNM) hidden in sea-going cargo containers has been identified as a significant threat at US ports, consequently several SNM detection schemes based on imaging and active interrogation techniques are being developed. Since it has proven difficult to establish what standard cargos should be, we analyzed shipping manifests for US imports shipped through North American ports collected on 14 days distributed over 12 months, and obtained several distribution functions of interest to the cargo scanning community, such as average densities, commodity categories, and packaging types. The "Nuclear Carwash", a cargo scanning technique currently under development at LLNL is based on neutron active interrogation, and relies on the unique signature of beta-delayed gammas emitted by fission products in the 3 to 7 MeV energy range. ¹⁹F(n,alpha)¹⁶N, has been identified as the main potential interference for neutrons in the 7 to 9 MeV range and estimates of cargo compositions based on manifests identified as containing fluorine are presented.