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开发了一种用~(238)U和~(232)Th作为内标的α能谱测定环境样品中铀和钍放射性同位素的新方法。应用中子活化分析技术精确地测定样品中的~(238)U和~(232)Th。将其他部分样品全部溶解,采用阴离子交换法分离铀和钍,制备为α能谱测定的电镀薄(低强度)源。从已知的~(238)U和~(232)Th质量浓度,求得它们的活度浓度,之后据α能谱,从U(~(234)U、~(236)U、~(238)U)和Th(~(228)Th、~(230)Th、~(232)Th)放射性同位素的比值中,获得同位素的绝对活度浓度。该方法的优点是对放射化学分离的化学回收率和α能谱仪的计数率都没有特殊要求。应用内标可以不需要外加昂贵的、经校准的放射性同位素指示剂(如~(232)U和~(229)Th)。用一些已检定的环境参考样试验了这种新方法,并且同外加放射性同位素指示剂的传统方法进行了比较。其优点是同标准方法相结合可获得一组独立的数据,用于质量控制。
A new method for the determination of uranium and thorium radioisotopes in environmental samples by α spectroscopy using ~ (238) U and ~ (232) Th as internal standards was developed. The neutron activation analysis technique was used to accurately determine the ~ (238) U and ~ (232) Th in the samples. The other parts of the sample were completely dissolved, and the uranium and thorium were separated by the anion exchange method to prepare a thin (low-intensity) source electrospun as measured by α-spectrometry. From their known concentrations of ~ (238) U and ~ (232) Th, their activity concentrations were determined. From the results of α spectra, ) U) and Th (~ (228) Th, ~ (230) Th, ~ (232) Th) radioactive isotopes. The advantage of this method is that there is no special requirement for the chemical recovery of radiochemical separation and the counting rate of alpha spectrometer. Application of internal standards may not require the addition of expensive, calibrated radioisotope indicators (such as ~ (232) U and ~ (229) Th). This new method was tested with some of the certified environmental reference samples and compared to the traditional method of adding radioactive isotopes. The advantage is that in combination with standard methods a set of independent data is available for quality control.