Determination of “” – the time elapsed since the last chemical purification – of a nuclear material is an important parameter in Nuclear Forensic analysis. Estimation of age may give crucial acumen of the possible production facility and the declared origin – if available – in case of a suspected nuclear material which is out of regulatory control. Mass spectrometry is the most common analytical technique used for chronological studies due to its superior precision (lower uncertainty). Though alpha spectrometry can be used for age determination, it better suits for irradiated fuel based radio-chronology because of higher specific activity of irradiated actinides (actinides formed by irradiation of actinides within a reactor) like plutonium. This paper describes the application of alpha spectrometry for the age determination in some natural U-metal samples with known history. The method utilises the radioactive non-equilibrium existing between U and Th isotopes in the sample for the elucidation of age of the material. Optimisation of a chemical procedure for the separation of ultra-trace amount of thorium isotopes from bulk uranium material using double column anion exchange chromatography is also presented. The chemical recoveries of uranium and thorium obtained with the present method were >95%. The uncertainty in age determination was <10% and ∼15% for older (∼51 years) and newer (∼11 years) samples respectively. The method is also used to elucidate the age of an unknown uranium material and found to be 39 ± 4 years old.

中文翻译：

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应用放射分析技术测定核材料“年龄”以进行核法证

确定核材料的“”（自上次化学纯化以来经过的时间）是核法证分析中的一个重要参数。如果可疑核材料不受监管，年龄估计可以为可能的生产设施和声明的来源（如果有的话）提供关键的洞察力。质谱法因其卓越的精度（较低的不确定性）而成为用于年代研究的最常用分析技术。虽然α能谱测定法可用于年龄测定，但它更适合基于辐照燃料的无线电年代学，因为辐照锕系元素（在反应堆内辐照锕系元素形成的锕系元素）如钚具有更高的比活度。本文介绍了 α 能谱测定法在一些具有已知历史的天然 U 金属样品中的年龄测定的应用。该方法利用样品中U和Th同位素之间存在的放射性非平衡来阐明材料的年龄。还提出了使用双柱阴离子交换色谱法从散装铀材料中分离超痕量钍同位素的化学程序的优化。用本方法获得的铀和钍的化学回收率>95%。对于较旧的（~51 岁）和较新的（~11 岁）样本，年龄确定的不确定性分别<10% 和~15%。该方法还被用来阐明一种未知铀材料的年龄，结果发现其年龄为 39 ± 4 岁。