A review of active neutron interrogation and related technologies for detection and identification of explosives and drugs: Challenges and perspectives

Abstract The detection of illicit cargo and hazardous materials within global logistics systems has become a high-security priority due to increasing and diversifying contraband. While modern X-ray and millimeter-wave imaging systems offer excellent throughput and structural visualization for inspection, they face inherent limitations in elemental identification and penetration through high-density cargo. Alternatively, neutron interrogation, which utilizes uncharged particles for inspection, exhibits superior penetration power compared to the other techniques and provides the elemental composition of subject materials through nuclear reactions. This article provides a comprehensive review of neutron-based active interrogation technologies developed over the past three decades for security screening. They are categorized into thermal neutron analysis, pulsed fast neutron analysis, the associated particle technique, and others, based on their physical principles and detectable signatures. Significant research initiatives from the United States, Europe, and Australia are examined, highlighting the transition from laboratory-scale proof-of-concept studies to field-deployable systems. This article discusses technical issues regarding detection sensitivity, inspection times, throughput, and spatial footprint required for radiation safety. Complementary technologies, such as photon interrogation with photoneutrons or nuclear resonance fluorescence, are also reviewed as potential solutions to these constraints. This article presents a perspective on the future evolution of technologies aimed at enhancing the reliability and feasibility of active interrogation in real-world security environments.