NUKLEONIKA 2010, 55(4):445-450



Jin Wang1,2,3, Oliver Meisenberg2, Yongheng Chen4, Erwin Karg2, Jochen Tschiersch2

1 Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,
Guangzhou 510640, PR China

2 Helmholtz Zentrum München, German Research Center for Environmental Health,
1 Ingolstädter Landstr., 85764 Neuherberg, Germany

3 Graduate School of the Chinese Academy of Sciences, Beijing 100049, PR China
4 School of Environmental Science and Engineering, Guangzhou University,
Guangzhou 510006, PR China

This study investigates filtration of air as potential mitigation method of thoron progeny exposure. The experiments were conducted in a model room (volume 7.1 m3) which was equipped with a pump and an HEPA (high efficiency particulate air) filter. Filtration at a rate of 0.2, 0.4, 0.5 and 0.8 h–1 during 88 h proved an effective practice in reducing the total indoor thoron decay product concentration. The results indicate that 0.4–0.8 h–1 filtration rate had almost the same filtration efficiency in decreasing the total thoron EEC (equilibrium equivalent concentration) by 97% while 80% of total thoron EEC were reduced by 0.2 h–1 filtration rate; meanwhile, the unattached thoron EEC rose significantly by 190, 270, 290%, respectively under 0.4–0.8 h–1 filtration rate, whereas 0.2 h–1 filtration rate increased unattached thoron EEC by 40%. The aerosol number size distribution variation reveals that filtration operation removes smaller particles faster or earlier than the larger ones. The annual effective dose calculated was reduced by 91–92% at a filtration rate of 0.4–0.8 h–1 while 75% reduced at 0.2 h–1 filtration rate after 88 h filtration process.

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