The study on accurate measurement of 220Rn activity concentration was carried out theoretically and experimentally. The effect of the volume of dryer vessel and the sampling flow rate on 220Rn measurement was studied in detail. It is found that the increase of dryer volume and the decrease of sampling flow rate can increase the differences between RAD7 results of 220Rn activity concentration and true value. For an accurate measurement of 220Rn activity concentration, the correction is necessary. And the results show that correction factors for both the RAD7 proper small dryer and the big dryer are 1. 224±0. 118 and 2. 232±0. 598, respectively.%针对RAD7测氡仪220Rn活度浓度准确测量的问题,本文采用理论模型分析和实验测量比较的方法,分析干燥管体积和采样泵流速对RAD7测氡仪220Rn活度浓度测量结果的影响.研究表明,随着干燥管体积增加和采样流速减小,RAD7测氡仪220 Rn活度浓度测量值同环境220Rn活度浓度真实值之间的差别增大.RAD7测氡仪采用小干燥管干燥时,修正因子R为1.224士0.118;采用大干燥管时,修正因子R为2.232±0.598.采用上述修正因子对RAD7测氡仪220Rn活度浓度测量结果进行修正,能在一定程度上解决RAD7测氡仪220 Rn活度浓度准确测量问题.
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