Impact of humidity and flowrate on the thoron measurement sensitivity of electrostatic radon monitors
Impact of humidity and flowrate on the thoron measurement sensitivity of electrostatic radon monitors
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DOI：
10.1088/1361-6498/acb067
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发表时间：
2023-01
影响因子：
1.5
通讯作者：
Chunyu He;Hao Wang;Lei Zhang;Q. Guo
中科院分区：
文献类型：
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作者：
Chunyu He;Hao Wang;Lei Zhang;Q. Guo
氡活度浓度的准确测量是氡暴露评价和降低其对氡测量影响的一个重要问题。对于基于静电采集技术和α光谱分析仪的氡监测仪，空气湿度和采样流量是影响氡活度浓度测量灵敏度的关键因素。为了提高钍的测量灵敏度和稳定性，本研究进行了系统的理论推导和实验研究。结果表明，随着绝对湿度的增加，钍的测量灵敏度呈负指数函数下降，在相同条件下，钍的灵敏度远低于氡的灵敏度，这主要是由于室内外钍浓度比值较小所致。当测量室空气交换速率（采样流量/内部体积）增大时，气体的测量灵敏度先快速增大后缓慢降低，在空气交换速率为0.24 s−1时达到最大值。在实际应用中，在正常换气速率范围内（如<0.05 s−1），增大采样流量可以大大提高测气量的灵敏度，是目前监测设备条件下更新测气量的有效途径。
The accurate measurement of thoron activity concentration is an important issue in both thoron exposure evaluation and in reducing its influence on radon measurement. For radon monitors based on electrostatic collection technique and an alpha spectrometry analyser, air humidity and sampling flowrate are key factors influencing the sensitivity of thoron activity concentration measurement. For the purpose of improving thoron measurement sensitivity and stability, theoretical derivation and experimental studies were systemically performed in this study. The results show that thoron measurement sensitivity decreases as a negative exponential function with absolute humidity increasing, and the sensitivity of thoron is much lower than that of radon under the same conditions, which is mainly caused by the small value of the concentration ratio of thoron inside to outside of the chamber. When the air exchange rate of the measurement chamber (sampling flowrate/inner volume) increases, the measurement sensitivity of thoron gas first increases rapidly and then decreases slowly after reaching its maximum at the air exchange rate of 0.24 s−1. In practice, in the normal air exchange rate range (for example <0.05 s−1), increasing the sampling flowrate could greatly improve the thoron measurement sensitivity, which consequently suggests an effective way to update thoron measurement under the present conditions of the monitor.