Intercomparison of activity size distribution of thoron progeny and a mixture of radon and thoron progeny

被引:19
作者
Cheng, YS
Chen, TR
Yeh, HC
Bigu, J
Holub, R
Tu, K
Knutson, EO
Falk, R
机构
[1] Lovelace Resp Res inst, Inhalat Toxicol Lab, Albuquerque, NM 87185 USA
[2] Canadian Ctr Mineral & Energy Technol, Elliot Lake, ON, Canada
[3] US Bur Mines, Denver, CO USA
[4] Swediah Radiat Protect Inst, Stockholm, Sweden
关键词
aerosol activity size distribution; radon decay product aerosols; thoron decay product aerosols; unattached fraction; intercomparison excercise results; intercalibration excercise results; condensation nucleus concentration (CNC);
D O I
10.1016/S0265-931X(00)00045-X
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The First International Intercomparison and Intercalibration Meeting for Thoron and its Progeny and Thoron/Radon Mixture was organized to compare techniques for determining concentrations and particle size distributions of Rn-220 and mixtures of Rn-222 and Rn-220. The meeting was held at Elliot Lake, Canada, November 2-6, 1992. We have reported results of activity size distributions and measurements of unattached fractions of both thoron progeny and mixtures of thoron/radon, Four teams, including the US Bureau of Mines in cooperation with Canada Center for Mineral and Energy Technology, the US Environmental Measurement Laboratory (EML), the Lovelace Respiratory Research Institute, and the Swedish Radiation Protection Institute (SSI) participated in the intercomparison of activity size distributions. Each team had a different diffusion sampling system and counting protocol. Results for all four systems were in good agreement when thoron gas was used in the test chamber. However, in the case of thoron and radon gas mixtures, the agreement among the different sampling systems was not as good. One reason for the inconsistency of results was that the sensitivity of the systems was different. Calculation of size distribution for individual progeny (Po-218, Pb-214, Bi-214, Pb-212, and Bi-212) requires sampling systems with improved sensitivity. Our results suggest those diffusion batteries with a minimum of four stages and more likely five stages are optimal In addition, a system for continuously counting the total alpha particles, such as the EML system, or alpha spectrometry, such as the SSI system, is needed. Our results provide a relationship between the unattached fraction and condensation nucleus concentration over a wide range of particles from 300 to 16,000 cm(-3). These findings are consistent with measurements obtained in indoor environments, mines, and underground caves, indicating that it is possible to establish a more universal relationship. (C) 2000 Elsevier Science Ltd. All rights reserved.
引用
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页码:59 / 78
页数:20
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