Monte Carlo Simulate and Design of Shied Structure of Am-Be Neutron Source

Abstract: The Am-Be neutron source is usually used in our experiment,which is made by the nuclear reaction(α,n)of ~(241)AmO_2 and Be powders.In order to analysis the online iron ore by the Am-Be neutron source,we need to slow and shield the Am-Be neutron sour ce.This paper contains the following two aspects:First,use the threshold detectors meth od to measure the neutron spectroscopy of Am-Be neutron source at the close place.Sec ond,we use MCNP-4C software to analog source spectrum at the same place,then com pared with the threshold detector measurement results,and evaluate the comprehensive pe rformance of the neutron moderation structure,at last we get the optimized project.After slowed,Am-Be neutron source has higher rate of low-energy neutron flux.Thr eshold detectors method measured neutron spectroscopy is a simple and very practical m ethod.Compared to other measurement methods,Threshold detector method has the adva ntage of spend less,insensitive to theγ-ray and slower threshold neutron,small size dete ctor,and less interference to the field under test.Monte Carlo Method can realistically describe the random events and simulate the e xperiment course.It is very suitable for the calculation of particle transport problem whi ch has the randomicity.The method has been widely used in the simulation of nuclear e xperiments include neutron detection.MCNP is a general program to simulate nuclear ex periments,which is made by Los Alamos Station Lab in USA based on the Monte Carl o thoughts.In the article author introduced Monte Carlo method,determined the content of simu lation,established the geometric model and the calculation model.The author also used t he MCNP-4C program to simulate and calculate Am-Be neutron source.The results show that first using metal lead to slow neutron,by the middle of the thickness of 30cm pol yethylene,neutron flux can be reduced to the original 10percent,then selecting the outer of the boron-containing paraffin moderation material with 10 percent B_4C by weight.Th e ulti-outer use 6.25 cm thick layer of iron,making shield aroundγtally lower than the perfect value. Based on the simulation of moderation shield structure of Am-Be neutron source,it is helpful to design a more rational device.It also helpful to design the moderation struc ture of other neutron source…
Key words: Am-Be neutron source; threshold detector; MCNP; moderation structure

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