非平衡态低浓铀样品富集度测量修正方法与时间校正  

A Correction Method and Its Time Correction for Enrichment Measurement of Non-Equilibrium Low-Enriched Uranium

作　　者：张可语 柏磊[1] 赵浩程 刘一帆 吕浩 ZHANG Keyu;BAI Lei;ZHAO Haocheng;LIU Yifan;LÜHao(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：《同位素》2025年第2期155-161,共7页Journal of Isotopes

摘　　要：铀富集度是核保障、核材料衡算的关键信息,通常基于衰变平衡原理利用^(235)U的185 keV能峰、^(238)U的子体^(234m)Pa的1001 keV能峰来测量分析^(235)U的富集度。但是在浓缩铀生产上,气体扩散法或离心法分离后子体与母体的平衡被打破,新分离得到的样品中子体的不断产生和衰变会使测得的含量不准确,如果直接利用^(238)U的子体^(234m)Pa的含量,会导致得到的结果有误差与实际富集度不符。为了能够对非平衡态的铀样品进行测量,本研究提出一种基于^(238)U的子体^(234m)Pa的时间修正方法,根据样品分离时间与衰变变化的关系经过时间修正得到处于非平衡态铀的富集度。使用该方法对分离时间为40 d左右、富集度为1.8%的六氟化铀气体进行分析验证,并将所得结果与PC/FRAM软件分析结果做对比。结果表明,该方法将富集度标称值偏差由平均47.5%降至4.1%,可实现根据分离时间对计算富集度较为准确的校正。The concentration of^(235)U is the key information for nuclear safeguards and nuclear material accountancy,and the enrichment of^(235)U is usually measured and analysed based on the principle of decay equilibrium using the 185 keV energy peak of^(235)U and the 1001 keV energy peak of^(234m)Pa of the daughter of^(238)U.However,in the production of enriched uranium,the equilibrium between the daughter and the parent body is broken after separation by gas diffusion method or centrifugation method,and the continuous generation and decay of the daughter in the newly separated samples make the measured content inaccurate,and the direct use of the^(234m)Pa content in the daughter of^(238)U leads to an error in the results obtained,which is not in line with the actual enrichment degree.In order to be able to measure uranium samples in nonequilibrium,this paper proposes a time-correction method based on the^(234m)Pa of the^(238)U substrate,which is based on the relationship between the sample separation time and the decay change to obtains the enrichment degree of uranium in nonequilibrium after the time correction from the relationship between the sample separation time and the decay change.The method was used to analyze and validate a 1.8%enriched UF6 gas with a separation time of about 40 days and compared the results with those obtained by PC/FRAM software.The results reduced the deviation from the nominal enrichment value from an average of 47.5%to 4.1%,achieving a more accurate correction of the calculated enrichment based on the separation time.

关 键 词：核保障 Γ能谱测量 铀富集度 非平衡态 

分 类 号：TL81[核科学技术—核技术及应用]