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Updated: Aug 6, 2026

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films
Published on: November 9, 2015
Size distributions of attached and unattached radon and thoron progeny in typical environments in China
Hao Wang1, Jinmin Yang2, Xiaotong Chen1
1Environmental Technology Division, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China.
Abstract:
Radon (222Rn, Rn) and thoron (220Rn, Tn) progeny are the primary contributors to natural radiation exposure. Accurate assessment of the radiological hazard from radon/thoron depends heavily on the characteristic parameters of these progeny, with particle size distribution identified as the most critical factor. However, systematic measurements of radon/thoron progeny size distributions remain very limited, mainly due to the insufficient attention given to thoron and the constraints of measurement sensitivity. Extensive field surveys were conducted in diverse environments in China with an 8-stage screen diffusion battery (SDB) system and a newly developed graded screen array (GSA) system. The results show that the activity median diameter (AMD) of attached radon progeny is 209 ± 16 nm (AMD¯±σAMD¯) indoors, 277 ± 26 nm in coal mines, 218 ± 20 nm in the investigated NORM (Naturally occurring radioactive material) environments and 189 ± 16 nm outdoors, with similar values observed for thoron progeny. Analysis of environmental factors indicated that ambient temperature, seasonal variation, and aerosol number concentration had minor effects on the AMD of attached progeny, while carrier aerosol size and sampling location exerted significant influences. The AMD of unattached progeny is 1.10 ± 0.15 nm for radon and 2.20 ± 0.20 nm for thoron. The results are expected to improve the accuracy of inhalation dose assessment and provide important input parameters for radiation protection models.
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