Pujol Ll, Suarez-Navarro J A
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT-DIAE), Avda. Complutense 22, 28040 Madrid, Spain.
Appl Radiat Isot. 2004 May;60(5):693-702. doi: 10.1016/j.apradiso.2003.10.013.
Two methods were used to apply self-absorption corrections for the determination of beta radioactivity in water samples (either for an identified radionuclide or for monitoring trends). One method was performed by estimating the absorption coefficient by assuming an exponential behaviour of absorption using external absorbers, while the other method was performed by preparing empirical curves using standards of different mass. In the first method, a relationship between absorption coefficient and maximum beta energy was also derived. In the second method, self-absorption curves for 90Sr/90Y standard were prepared with several sodium salts (carbonate, nitrate and sulphate salts) and, for 40K standard using a potassium salt. Both beta emitters are usually necessary to calibrate detectors for beta radioactivity measurements. This study showed that, for 90Sr/90Y, results using standards of different mass were more accurate than using external absorbers. Furthermore, it is highly recommended to melt sodium nitrate salts in order to perform a self-absorption curve for 90Sr/90Y because standards were stable in time and homogeneously distributed. For 40K, a self-absorption curve may be easily derived using paper absorbers of different thickness, instead of performing a time consuming self-absorption curve using a set of varying thickness of 40K standards. In order to test the two methods, the gross beta activity of several environmental water samples was analysed.
采用两种方法对水样中的β放射性进行自吸收校正（用于确定特定放射性核素或监测趋势）。一种方法是通过使用外部吸收体假设吸收呈指数行为来估算吸收系数，而另一种方法是使用不同质量的标准品绘制经验曲线。在第一种方法中，还推导了吸收系数与最大β能量之间的关系。在第二种方法中，用几种钠盐（碳酸盐、硝酸盐和硫酸盐）制备了90Sr/90Y标准品的自吸收曲线，并用钾盐制备了40K标准品的自吸收曲线。在β放射性测量中，通常需要这两种β发射体来校准探测器。本研究表明，对于90Sr/90Y，使用不同质量标准品得到的结果比使用外部吸收体更准确。此外，强烈建议熔化硝酸钠盐以绘制90Sr/90Y的自吸收曲线，因为标准品在时间上稳定且分布均匀。对于40K，可以使用不同厚度的纸质吸收体轻松推导出自吸收曲线，而不必使用一组不同厚度的40K标准品来绘制耗时的自吸收曲线。为了测试这两种方法，分析了几个环境水样的总β活性。
