土壤样品中总α测量刻度方法探讨

Study on α ray measurement and calibration of soil samples

土壤样品中总α测量采用厚源法,仪器通过刻度后,对样品进行测量。通过对土壤样品成分的分析,选择两种刻度源——241Am源和编号为GBW04127的铀钍天然系矿石标准物质分别对低本底α、β测量仪进行刻度,用9个国家标准物质模拟土壤样品,通过数据对比可知:对于用混合源作为验证源来说,用GBW04127作为刻度源比用241Am测量结果更为准确,误差由20%~40%降至20%以内;对于其它标准样品,误差并没有得到改善,多数反而增大。因其成分组成与真实的土壤有较大差距,土壤中不单一含有U、Th或K成分,混合源与真实的土壤放射性成分更接近,更能代表土壤样品。因此,土壤样品中总α测量刻度源可以考虑使用编号为GBW04127的铀钍天然系矿石标准物质。

For total alpha measuring of soil samples, we use thick source method. After calibration of the instrument, we measure the samples. Through analysis on composition of the soil sample, we choose two calibration sources to calibrate the instrument （Low Background α and β measuring device） respectively-source of ^241Am and numbers for GBW04127 standard materials （natural uranium and thorium ore）. 9 standard materials was used to simulate the soil samples. By comparison of the data, it was found that for mixed source samples, the result of using GBW04127 source as calibration source is more exact than ^241Am, the error from 20% to 40% decrease to 20%. For other standard samples, the errors are not improved, most of them have increased. Because its components has a large gap with real soil. The soil is not only composed of a single contains U, Th or K ingredients. Because mixed source sample is closer to the real soil ingredients, and more suitable for the soil sample. Therefore, for total alpha measuring of soil samples, GBW04127 standard materials （natural uranium and thorium ore） was recommended as calibration source.