铀富集度测量中相对效率曲线拟合修正方法  

Correction Method of Relative Efficiency Curve Fitting in Uranium Enrichment Measurement

作　　者：赵浩程 柏磊[1] 韩苗苗 范潇 张俞奇 ZHAO Haocheng;BAI Lei;HAN Miaomiao;FAN Xiao;ZHANG Yuqi(China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院,北京102413

出　　处：《原子能科学技术》2023年第10期2016-2025,共10页Atomic Energy Science and Technology

摘　　要：相对效率刻度法是核保障现场视察中测量样品铀富集度的常用手段,其核心是对样品相对探测效率的曲线拟合。本文基于同轴型高纯锗探测器的实际表征结果,利用蒙特卡罗方法模拟得到探测器点源情况下的相对探测效率,通过对比3种拟合公式的拟合结果及误差,分析不同公式在富集度计算所用能区范围的拟合适用性;针对现场视察中常遇到的铝、不锈钢屏蔽及样品体源自吸收情况,进一步模拟其对样品相对探测效率的影响,考察曲线拟合效果,并通过添加修正因子对较厚屏蔽及强自吸收情况下的拟合曲线进行了修正。研究结果表明,添加修正因子后,不同屏蔽及自吸收情况下的相对效率拟合曲线在富集度计算所用特征峰处的拟合误差从2%~4%降到了1%~2%,提高了样品铀富集度的测量准确性。Gamma-ray spectrometry uses the X-ray and characteristic gamma-rays associated with 235 U,238 U and their decay daughters in uranium samples for analytical calculations to achieve rapid and timely nondestructive detection of sample enrichment.As one of the methods for determining uranium enrichment by gamma-ray spectrometry,the relative detection efficiency calibration method has been commonly used in nuclear safeguards on-site inspections to measure the enrichment of samples.Its core is the relative efficiency self-calibration using multiple characteristic gamma-rays of 235 U in the low energy region of 120-186 keV and the characteristic gamma-rays of 238 U decay daughter 234 Pa m in the high energy region of 258-1001 keV.In this paper,the relative detection efficiency of the detector was obtained using the Monte Carlo method based on the actual characterization results of a coaxial-type high-purity germanium detector,the fitting results and errors of three different types of fitting formulas in different energy region ranges were investigated.A comprehensive analysis of the effect of the fitting formulas from the low-energy region to the medium-high energy region on the relative efficiency of the characteristic peaks shows the logarithmic transfer series function performs better results among the three fitting formulas.During the on-site inspection,the aluminum and stainless steel shieldings of the sample and the self-absorption of the uranium dioxide and uranium hexafluoride body source have a certain impact on the relative detection efficiency curve.The specific influence and changing trend of these factors on the curve were studied,and the fitted curves for thicker shields and strong self-absorption were then corrected by adding correction factors.The results show that after adding the correction factor,the fitting error of the relative detection efficiency curve for different shielding and self-absorption cases is reduced from 2%-4%to 1%-2%at the characteristic peaks used for enrichment calculation.The resu

关 键 词：核保障 现场视察 相对探测效率 铀富集度 

分 类 号：TL81[核科学技术—核技术及应用]