Laboratory tests of the C-BORD Rapidly Relocatable Tagged Neutron Inspection System

In the frame of C-BORD project (H2020 program of the EU), a Rapidly Relocatable Tagged Neutron Inspection System (RRTNIS) has been developed for nonintrusive inspection in cargo containers aimed at explosives and other illicit goods detection. Twenty large volume NaI detectors are used to determine the elements composing inspected materials from their specific gamma spectra signatures induced by fast neutrons. The RRTNIS inspection is focused on a specific suspect area selected by X-ray radiography. An unfolding algorithm decomposes the energy spectrum of this suspect area on a database of pure element gamma signatures. A first classification is performed between inorganic materials like metals, ceramics or chemicals, and organic materials like wood, fabrics or plastic goods. Concerning organic materials, the obtained elemental proportions of carbon, nitrogen, and oxygen allow discriminating explosives from illicit drugs and benign substances. This paper reports on the final laboratory tests performed at CEA Saclay, France, to assess the RRTNIS detection performances before further demonstration tests in a real seaport environment. Simulants of explosives and illicit drugs have been hidden at different depths inside iron or wood cargo materials, which are representatives of the different neutron and gamma attenuation properties encountered in real cargo containers. Hundreds of experiments have been performed, showing that a few kg of explosives or narcotics can be detected by the RRTNIS in 10 min inspections.