活化法测量中子活化在线分析系统样品处的中子能谱
Neutron Spectrum Measurement with Activation Method in Sample Place of Online Neutron Activation Analysis System
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摘要: 用多箔活化法测定了由AmBe中子源慢化屏蔽系统构成的中子活化在线分析系统样品处的中子能谱。 根据待测场点的中子注量率水平， 选用了5种非裂变核材料箔， 其中4种是中能区和热区的， 1种是快区的， 给出了各箔片的特性参数。 通过在待测场点对箔片进行辐照， 并测量其生成放射性核的γ放射性， 计算出了各箔片的活化率。 运用SANDII和MSIT迭代方法， 解出了待测场点的中子能谱。 详细分析了数据处理过程中群截面的加工处理以及由于自屏蔽效应引起的群截面修正问题； 研究了影响解谱精度的主要因素； 对解谱结果作了一定的分析讨论； 并用蒙特卡罗(MC)方法对最后的中子能谱做了不确定度分析。Abstract: The neutron spectrum in sample place of online neutron activation analysis system was measured with multiple foil activation technique. According to the neutron fluence level of measuring request， 5 kinds of nonfission nuclear material foils were selected， of which 4 were sensitive to thermal energy region and intermediate energy region， and 1 was sensitive to fast energy region. By measuring the foil activity， the neutron spectrum that was needed to measured was unfolded with the iterative methods SANDII and MSIT. Meanwhile， the process of producing and modifying group cross section were analysed amply. The main factors which have influence on the accuracy of the solution were studied. The discussion for solution was done simply， and the uncertainty of solution was analysed by using the Monte Carlo method.
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