Design and Optimization of Neutron Moderation Device for Thermal Neutron Analysis Landmine Detection

Key words: 
• TNA landmine detection /
• ²⁵²Cf neutron source /
• neutron moderation

Abstract: Compared with the traditional landmine detection methods, Thermal Neutron Analysis (TNA) landmine detection has the advantages of high accuracy, low false alarm rate and strong adaptability to the environmental change.But the long detection time restrict the wide application of this technology. In order to shorten the detection time, one possible design of neutron moderation device based on 252Cf neutron source is proposed to enhance the moderated neutron
flux in mine position. The device consists of four parts, the neutron moderator, the neutron reflector, the background shield and the useless neutron absorbing layer. Then, the performance of four widely used materials in neutronics was compared with MCNP5 code, and HDPE was chosen as the neutron moderator material, graphite as the neutron reflector material. The thickness of the useless neutron absorbing layer was optimized at the same time. Finally, an experimental platform of 252Cf neutron moderation device was assembled on the basis of simulation results, and a series of experiments were carried out to optimize the geometric dimensions and evaluate the dose equivalent with two different strengths neutron source, 10⁴ and 10⁷ n/s. The results indicate that this device can effectively enhance the thermal neutron flux at mine position by more than 11 times and ensure the radiation safety.