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Dose assessment from the exposure to attached and unattached progeny of radon and thoron in indoor environment

Prasad M., Bossew P., Kumar G. A., Mishra R., Ramola R. C.

Acta Geophysica

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2018

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Vol. 66, no. 5

1187--1194

EN

The radiation dose from the exposure to radon (222Rn) and thoron (220Rn) is mainly contributed by their progeny, not by the gases themselves. This study aims to investigate the health risk associated with the internal exposure to attached and unattached progeny of 222Rn and220Rn in the indoor environment of Garhwal Himalaya, India. For this purpose, the passive measurements of attached and unattached progeny levels of 222Rn and 220Rn were performed in Garhwal Himalaya, India using nuclear track detector based recently developed progeny sensors. The measured values of unattached and total progeny concentrations were used to estimate the unattached fractions and annual effective doses. The annual mean unattached fractions of 222Rn and 220Rn progeny were found to be 0.15 ± 0.04 and 0.17 ± 0.05, respectively. The estimated values of the annual effective doses were found to be 3.4 ± 1.9 mSv/y and 0.7 ± 0.4 mSv/y due to the progeny of 222Rn and 220Rn, respectively. The methodology and results obtained are discussed in details.

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Studies of the radon progeny particle size distributions in the domestic environment. Epidemiological and dosimetric dose estimates

Mamont-Cieśla K., Stawarz O.

Nukleonika

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2012

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Vol. 57, No. 3

411-420

EN

Measurements of the short-lived radon progeny particle size distributions were performed under realistic natural conditions in 54 dwellings in 6 regions of Poland by means of the Radon Progeny Particle Size Spectrometer (RPPSS). The RPPSS comprises a one open face stage, a 4-stage diffusion battery and a 3-stage multi-hole inertial impactor. It was manufactured at the ARPaNSA (Melbourne, Australia), under supervision of Dr S. B. Solomon and supplied with his software. While using the continuous mode, the programme provides analysis of the potential alpha energy concentration on each stage, particle size distributions and weighted dose conversion factors based on the ICRP human respiratory tract model (HRTM) as implemented in the computer code RADEP (radon dose evaluation program). The unattached fraction indoors ranges from ca. 0 to 53% with an arithmetic mean and median of 17%. The equilibrium factor F was observed in the range from 7 to 64% with an arithmetic mean of 32% and median of 29%. The annual effective doses from radon progeny for the general population were estimated according to two models: epidemiological and dosimetric. The mean values of the ratios of the dosimetric to epidemiological dose estimates for the general population (breathing rate 0.78 m3/h) and workers (breathing rate 1.2 m3/h) are 1.0 and 1.4, respectively. The epidemiological dose estimates for the general population are smaller in comparison with the dosimetric estimates for the unattached fraction fp greater than 17%. It was shown that the dependence of the ratio of the doses estimated on the basis of two models on the unattached fraction fp is well described by a linear equation.

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First results of measurement of equilibrium factors F and unattached fractions fp of radon progeny in Czech dwellings

Jílek K., Thomas J., Tomášek L.

Nukleonika

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2010

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Vol. 55, No. 4

439-444

EN

The unattached fraction of radon decay product clusters fp and equilibrium factor F are dose relevant parameters in all dosimetric approaches to dose calculation. In the past, three year continuous weekly measurements of unattached and attached activity of radon daughter product and air exchange rate were carried out during heating season in 30 occupied typical Czech family houses. The results indicated significantly different weekly averages of equilibrium factor F and fp for houses located in towns compared those in villages. Due to this fact, approximately a 10 per cent average increase of equivalent lung dose rate was estimated in the detriment in towns. Average values of equilibrium factor F and fp were 0.40 and 8.6 per cent in urban houses and 0.32 and 10.7 per cent, respectively in rural houses. Based on the measurements of mean values of fp, average effective dose conversion factors (DFC) in units of mSv per working level month (WLM) were estimated to be 15.0 mSv/WLM in urban houses and 15.9 mSv/WLM in rural houses, respectively.