圆柱体源自吸收修正的数值计算方法研究

Research on Numerical Calculation Method of Cylindrical Source Self-Absorption Correct

在对放射性样品进行定量分析时,样品的自吸收效应会导致测量结果出现偏差。分析了应用较为广泛的简化计算模型算法的适用范围及缺陷,提出了一种基于理论分析和数值积分的圆柱形体源自吸收修正模型。通过对体源和探测器的精确建模,综合分析γ射线的空间立体角范围、在体源中的线衰减系数和总穿透路径,采用数值积分的方法求得了体源自吸收修正因子。计算了两个典型放射性核素131I和137Cs特征γ射线在不同尺寸探测器下的自吸收修正因子,与蒙特卡洛模拟结果进行对比,最大相对偏差不超过2%,得到了良好的一致性。最后,通过控制变量的方法使用该模型分析了体源自吸收效应的影响因素及修正方法,并重点分析了探测器尺寸对体源自吸收修正的影响。

In the quantitative analysis of radioactive samples,the self-absorption effect of the sample can lead to biased measurement results.The applicable scope and defects of the widely used simplified calculation model algorithm are analyzed,and a modified model of cylindrical source absorption based on theoretical analysis and numerical integration is proposed.Through the accurate modeling of the volume source and the detector,the spatial solid angle range of theγ-ray,the linear attenuation coefficient in the volume source and the total penetration path are comprehensively analyzed,and the volume-derived absorption correction factor is obtained by the method of numerical integration.The self-absorption correction factors of the characteristicγ-rays of two typical radionuclides~(131)I and~(137)Cs under different sizes of detectors are calculated.Compared with the Monte Carlo simulation results,the maximum relative deviation is not more than 2%,and good consistency is obtained.Finally,by controlling variables,the model is used to analyze the influencing factors and correction methods of the volume-derived absorption effect,and the influence of the detector size on the correction of the volume-derived absorption effect is analyzed.