放射性氙测量中的天然源γ谱仪校准技术

摘要

In order to satisfy the need of OSI (on-site inspection) ,the equivalent gas radioactive source was developed ,which was used to implement the efficiency calibration for 133 Xe 81.0 keV γ-ray .The radioactive source was composed of foam grains as matrix material and 226 Ra as parent nuclide ,and encapsulated by stainless steel and carbon fiber window to decrease the attenuation of γ-ray . The experiments on tightness and uniformity were done after the source was manufactured . When the source became equilibrium between 226 Ra and 214 Pb ,the efficiencies of X-ray of 214 Pb were measured . Then the interpolation calculation with determination values was done to obtain the efficiency of 133Xe 81.0 keV γ-ray .To verify the accuracy of calibration results ,the experiment was finished on the same measurement conditions with a 155 Eu source whose matrix and geometry dimensions were the same as 226 Ra source .The result indicates that the relative deviation of detection efficiency between 155 Eu 86.5 keV γ-ray and 214 Pb 87.3 keV X-ray is less than 1.0% .%基于禁核试核查现场视察的需求，研制了用于放射性氙测量的模拟气体源，实现了133 Xe 81.0 keVγ射线的效率校准。放射源基质为聚苯乙烯泡沫颗粒，母体核素为226 Ra ，采用不锈钢外壳封装，同时采用碳纤维窗以减少射线的衰减。放射源研制完成后，对其进行气密性和均匀性检验。当放射源达到平衡后，测量214 Pb的特征X射线的探测效率，然后插值计算得到133 Xe 81.0 keV γ射线的探测效率。为检验校准结果的正确性，制作了一个基质和几何尺寸均与226 Ra源相同的155 Eu放射源，并在相同测量条件进行了实验。结果表明，155 Eu 86.5 keV γ射线和214 Pb 87.3 keV X射线的探测效率之间的相对偏差小于1.0％。