电感耦合等离子体质谱测定铀样品年龄方法研究

Age Dating of Uranium Sample by ICP-MS

铀样品年龄与生产时间密切相关,是核法证学调查核材料来源属性的一个重要参数。本文研究建立了利用230Th/234U原子数比测定铀样品年龄的分析方法。分别用229Th和233U稀释剂进行铀样品同位素稀释,利用TEVA树脂对样品中的铀和钍进行分离处理,用多接收电感耦合等离子体质谱测量229Th/230Th和233U/234U原子数比,根据铀年龄计算公式通过230Th/234U原子数比可得到样品的铀年龄。采用该方法对CRM U850和U010标准样品进行了年龄测定,结果与美国劳伦斯·利弗莫尔国家实验室的测量结果一致,但较实际年龄偏大,可能是由于生产时纯化过程不完全,导致有残留的230Th在样品中。本文所建立的方法可用于铀样品230Th-234U模型年龄的测定,为核法证学调查提供重要信息。

Uranium age of sample is relevant to determine the date of production of the material and important to identifying the source of the material in nuclear forensics investigations.An analytical method for age dating of uranium-based nuclear materials by the measurement of 230 Th/234 U atomic ratio was developed.Uranium samples were diluted with 229 Th and 233 U spike respectively.Uranium and thorium in the samples were separated with TEVA resin.The atomic ratios of 229 Th/230 Th and 233 U/234 U were measured by multi-collected inductively coupled plasma mass spectrometry(MC-ICP-MS).The uranium age of the samples could be obtained by 230 Th/234 U atomic ratio according to the calculation formula of uranium age.The age of CRM U850 and U010 standard samples was determined.The results are consistent with those obtained by Lawrence Livermore National Laboratory in the United States.However,the results of both methods are older than the actual age.It was probably due to the incomplete purification process during production,which resulted in the residual 230 Th in the samples.The established method can be used to determine the 234 U-230 Th model age of uranium samples and provide important information for verification investigation.