宽能域γ能谱测井系统结构参数优化设计研究

A study of structural optimization design of the wide-energy range gamma spectra logging system

伽马能谱测井广泛应用于放射性矿床、金属、非金属矿床、地层对比等方向,是我国目前铀矿资源勘查的主要方法。为获得更宽的伽马能谱测量范围,采用LaBr3和BGO双探测器组合来完成宽能域伽马能谱测井系统的设计,基于MCNP模拟研究宽能域伽马能谱测井系统的结构优化设计原则。探测器采用管式结构,屏蔽体采用钨铁镍合金效果最好,屏蔽体厚度达到14 cm时即可对远侧探头产生较好的屏蔽效果;近侧探头在相对位置在35 cm及以上时对快中子的屏蔽效果与远侧探头的效果相接近;改变中子源位置对热中子的屏蔽效果提升有限;硼单质作为热中子屏蔽体在厚度达到0.2 cm时即可达到较好的屏蔽效果。分析模拟所得数据可知:快中子的屏蔽效果主要由屏蔽体材料、厚度和近端探头与屏蔽体的距离决定,中子源与屏蔽体距离增加所起作用有限。

The gamma spectrometry logging is widely used in survey of radioactive,metallic and non?metallic deposits and stratigraphic correlation.In order to obtain a wider energy range of gamma spectra,the authors designed the wide?energy spectra logging system with the combination of LaBr3 and BGO detectors.To determine the optimal selection principle of the wide?energy range gamma spectra log?ging system,the authors built a model of wide?energy spectra logging system on MCNP to simulate the measured gamma spectrum.The simulation shows that the best effect is achieved when the shield is made of tungsten?iron?nickel alloy.When the shield thickness rea?ches 14 cm,simulation shows better shielding effect for the distal detector.The effect for the proximal detector is close to the distal one when its relative position is 35 cm or more.The effect of changing the position of the neutron source on the thermal neutron shielding is limited.As a thermal neutron shield,boron could achieve obvious shielding effect with 0.2cm layer.The effect of fast neutron can be re?duced by increasing shield thickness and the distance between the proximal detector and the shield.