Preventing the proliferation of highly enriched uranium (HEU) is an important issue all over the world. The active interrogation of HEU hided in the suitcase based on neutron technique is studied by using MCNP5 code. The neutron source of the detection system is based on the NG-9 neutron generator developed by Northeast Normal University. A set of HEU detection devices has been established. Lead is a kind of neutron-multiplier material with high density, so the lead block is chosen as the substitute for HEU. The size of the aluminum alloy suitcase is 58 cm × 42 cm × 25 cm. The NG-9 D-T neutron generator is placed on the suitcase. A lead block measuring 26.5 cm × 12 cm × 1 cm is placed in the center of the suitcase. The lead block has a density of 11.35 g/cm and a mass of approximately 3.6 kg. Daily clothes are placed inside the suitcase as a distraction. A cylindrical BGO detector with a diameter of 7.2 cm, a height of 29.7 cm is placed close to the suitcase to record gamma rays. A cylindrical lead shield with a thickness of 5 cm is placed outside the BGO detector. Paraffin wax is placed around the whole detection device to protect the neutron radiation and avoid the interference of other substances on the detection results. The purpose of this experiment is to verify the agreement of the MCNP5 simulation results and the experimental results. In this paper, threshold energy neutron analysis (TENA), fast neutron method, and thermal neutron method are used to detect HEU. The simulation results show that the presence of HEU in the suitcase can be determined by neutron flux which is higher than those in the absence of HEU.

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