SIMS测定玻璃固化样品中铀分布的分析方法研究

玻璃固化是一种常用的高放废液固化方法,其优点在于具有较高的抗化学介质侵蚀的能力和很好的辐照稳定性、热稳定性和机械稳定性,其不足之处在于抗水浸出等性能有所下降而使其安全性需要进一步通过抗浸出实验来进行衡量和确认。使用二次离子质谱(SIMS)分析玻璃固化体中的放射性成分(如铀元素)的分布及浸出行为等各项指标,是一种评估玻璃固化体抗浸出性能的分析手段。本文应用SIMS测试模拟玻璃固化体,以碳作为镀膜材料通过真空蒸发镀碳的方法优化样品制备条件,有效地解决了样品导电性差的问题,~(235)U/~(238)U同位素测定结果约为7.9‰±0.395‰,基本符合制作模拟样品时所使用的天然铀的同位素特征(~(235)U/~(238)U参考值约7.3‰)。研究表明,建立的方法实现了铀元素同位素丰度的测量,能直接显示铀的分布情况,该方法可为研究玻璃固化体中放射性元素的浸出行为提供一定的技术支持。

Determination of the Distribution of Uranium in Glass Solidified Samples by Secondary Ionization Mass Spectrometry

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) was commonly used to analyze trace elements in magnetite, which can be divided into internal standard (IS) and no internal standard (NIS) methods according to the calibration techniques. IS method involves a relatively complex process that determination of Fe contents by Electron Microprobe. Moreover, element contents will be affected by the analytical accuracy of IS element iron. In this study, analytical method for determining trace elements by LA-ICP-MS using multiple external standards (basaltic glasses BCR-2g, BIR-1g, BHVO-2g, GSE-1G) without an IS was developed. The proposed method avoids the determination of IS element. Trace element compositions of komatitic glass (GOR-128g) and natural magmatic magnetite (BC 28) were determined by the method and used to evaluate the reliability of the method. Results show that the analysis values of komatitic glass are consistent with the certified values and reported values by IS method. The relative standard deviation (RSD) of most elements is smaller than 5%. Most elements of natural magmatic magnetite have RSD better than 7% between the analysis values and the certified values, and have RSD better than 15% between the analysis values and the reported values by IS method. This indicates that multiple external standards without an IS method can realize the accurate calibration of trace element concentrations of iron-rich silicates and magnetite, overcoming the matrix effects. Therefore, multiple external standards without an IS method is a fast and precise method for determining trace elements in magnetite, which has a great application potential.