Study On The Moderation Shield Structure Between Neutron Source And Detector In Reflection Type Coal Analysis

Currently, Neutron Induced Prompt Gamma-ray Analysis technique has beenwidely applied in the field of elemental analysis of materials. In the coal qualitytesting it has already been successfully applied.In this paper, γ-ray shielding material outside BGO detector and its thickness isfirstly studied by MCNP-4C, and then the neutron moderator material between D-Tneutron generator and γ-ray shielding material is also studied by MCNP-4C.First, we establish a physical model which is to be simulated according to thebasic structure of the coal-line analysis device. We make a detailed simulation andcalculation for the above problems by MCNP-4C. The outside BGO detector is γ-rayshield and the peripheral of γ-ray shield is neutron protection body that the thicknessof them can be changed, The distance between the neutron generator and detectorchanges as the thickness change. The top of the detector is conveyor belt and wearplates which thickness is2cm, above the conveyor belt is20cm thick coal seam, the8cm thick vacuum layer is on the top of the coal seam, above it is2cm thick leadshield which is used to protect the reflective part of γ rays.MCNP simulation results show: the8cm thick lead outside BGO gamma-raydetector can effectively shield the interference gamma rays. It is that places11cm~15cm thick iron between D-T neutron generator and gamma-ray shield can quicklyreduce14MeV neutron energy that come from neutron generator, make it less than thethreshold of the elastic reaction between oxygen and neutron, can improve themeasurement accuracy of the oxygen in coal.The results calculated using MCNP-4C, applied to coal-line analysis anddetection device design, will improve the measurement accuracy of the field testing ofcoal.