摘要
适当的放射性核素快速检测方法对于具有流量大和计数率水平低特征的海关放射性安检等场景是必要的。相较于传统不确定性分析方法,贝叶斯方法和序贯概率比检验可充分利用测量物理量的全部信息而所需的样本量较少,基于此提出了一种新型序贯贝叶斯核素快速检测方法,分别在低辐射本底环境和自然辐射本底环境,使用一套LaBr3(Ce)探测系统和一组标准点源对该方法的可行性、检测性能和普适性开展了实验研究,并探究了方法的关键参数中第一类错误概率α、第二类错误概率β和时间间隔下限τmin对检测性能的影响。在本底计数率分别为59.3 s^(-1)和165.9 s^(-1)的两类本底环境中,α和β分别不超过0.1和0.01的条件下,实验结果显示:在无源情况下,该方法对本底辐射的平均检出时间分别为24.08 s和10.54 s,平均检出样本量分别为1427和1742,且发生误报后均可快速自适应消除并做出有效判决;在有源情况下,实验测量检测灵敏度下限分别约为8.2%和6.1%,对应的平均检出时间分别为8.59 s和6.61 s,实验测量漏报率均为0,平均检出时间只与全谱净计数率有关,平均检出样本量只与放射源信号的计数率信噪比有关,检测灵敏度下限可理论计算且与实验结果相吻合;参数τ_(min)的减小会增大检测灵敏度下限和减小检出时间,参数α和β可决定实验测量误报率和漏报率。研究表明本方法非常适用于低水平放射性核素的快速检测。
[Background]Appropriate fast detection method for radionuclides is necessary for customs radioactive security inspection with high flow rates and low counting rate levels.Compared with the traditional uncertainty analysis method,the Bayesian method and the Sequential Probability Ratio Test can fully utilize all the information of measured physical quantities and reduce the required sample size.[Purpose]This study aims to develop a new method to solve the problem of the fast and accurate detection of radionuclides at low radioactive counting rate scenarios.[Methods]A new Sequential Bayesian fast detection method for radionuclides was proposed on the basis of binary hypothesis H0(no radionuclides)and H1(radionuclides).Based on the principle that the time interval between adjacent two rays was exponential distributed,the decision was caculated by collecting a series of ray time samples in chronological sequence,and decisions were made by comparing the decision function with the preset upper and lower thresholds.Finally,experimental verifications were conducted on the feasibility,detection performance,and universality of the method by placing a set of standard point sources at different distances from the front of a LaBr_(3)(Ce)detection system in both low and natural radiation background environments.The effects of the key parameters of the method on the detection performance were investigated.[Results]Under the absence of radionuclides in two type of background radiation environments,the average detection time for background radiation by this method is 24.08 s and 10.54 s,with an average detection sample size of 1427 and 1742,respectively.Under the presence of radionuclides in two type of background radiation environments,the lower limits of detection sensitivity of experimental measurements are 8.2%and 6.1%,respectively,the corresponding average detection times were only 8.59 s and 6.61 s respectively,and the experimental measurement false negative rates were all zero.[Conclusions]Results of this study verify that above proposed method is very suitable for fast detection of low-level radionuclides.
作者
万琳健
张璇
张春雷
黄建微
柳加成
张晓乐
李德红
杨智君
WAN Linjian;ZHANG Xuan;ZHANG Chunlei;HUANG Jianwei;LIU Jiacheng;ZHANG Xiaole;LI Dehong;YANG Zhijun(College of Nuclear Science and Technology,Beijing Normal University,Beijing 100875,China;Institute of Ionizing Radiation Metrology,National Institute of Metrology,Beijing 100013,China;Nuclear and Radiation Safety Center,Ministry of Ecology and Environment,Beijing 102400,China)
出处
《核技术》
北大核心
2025年第1期102-114,共13页
Nuclear Techniques
基金
中国计量科学研究院基本科研业务费(No.AKYCX2315)资助。
关键词
序贯贝叶斯方法
放射性核素快速检测
二元假设
检测灵敏度下限
Sequential bayesian method
Fast detection for radionuclides
Binary hypothesis
Lower limit of detection sensitivity
