Radiological and Environmental Safety Division, Indira Gandhi Center for Atomic Research, Kalpakkam, Tamilnadu, India.
Homi Bhabha National Institute, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, Tamilnadu, India.
Radiat Prot Dosimetry. 2020 Jul 13;189(2):182-189. doi: 10.1093/rpd/ncaa029.
The radon (222Rn) and thoron (220Rn) fluxes from the soil and building materials are the major contributors to their indoor levels. Hence, the measurement of radon and thoron exhalation rates from the source matrix becomes the foremost step in controlling the indoor radon and thoron exposure. It is a challenge to measure the exhalation rates without disturbing the natural conditions. The back-diffusion phenomenon modifies the exhalation rate. The work presented here is to measure the back-diffusion coefficient and takes it into consideration while estimating the exhalation rate. For radon measurements, the back-diffusion coefficient and the free exhalation rates were simultaneously estimated by adopting a novel methodology. The leak rate of the experimental setup measured by this methodology was agreeable with the value measured by adopting the standard technique. In the case of thoron, the back-diffusion effect was found to be negligible for the present experimental conditions and it is duly explained. The above results were obtained by analyzing two soil samples with high 238U and 232Th content collected from monazite-rich coastal area.
氡（222Rn）和钍射气（220Rn）从土壤和建筑材料中的通量是其室内水平的主要贡献者。因此，测量源矩阵中氡和钍的呼出率成为控制室内氡和钍暴露的首要步骤。在不干扰自然条件的情况下测量呼出率是一项挑战。反扩散现象会改变呼出率。这里介绍的工作是测量反扩散系数，并在估算呼出率时考虑到它。对于氡测量，通过采用一种新的方法同时估计了反扩散系数和自由呼出率。通过这种方法测量的实验装置的泄漏率与采用标准技术测量的值一致。在钍的情况下，发现反扩散效应在目前的实验条件下可以忽略不计，并对此进行了适当的解释。上述结果是通过分析从富含独居石的沿海地区采集的两个具有高 238U 和 232Th 含量的土壤样品得到的。
