title: Preliminary Experiments Using a Passive Detector for Measuring Indoor 220Rn Progeny Concentrations with an Aerosol Chamber.
abstract: This paper describes preliminary experiments using a passive detector for integrating measurements of indoor thoron (²²⁰Rn) progeny concentrations with an aerosol chamber. A solid state nuclear detector (CR-39) covered with a thin aluminum-vaporized polyethylene plate (Mylar film) was used to detect only alpha particles emitted from ²¹²Po due to ²²⁰Rn progeny deposited on the detector surfaces. The initial experiment showed that Mylar film with area density of more than 5 mg cm⁻² was suitable to cut off completely alpha particles of 7.7 MeV from ²¹⁴Po of ²²²Rn progeny decay. In the experiment using the passive detector, it was observed that the net track density increased linearly with an increase of time-integrating ²²⁰Rn progeny concentration. As a result of dividing deposition rates by atom concentrations, the deposition velocity was given as 0.023 cm s⁻¹ for total ²²⁰Rn progeny. The model estimates of deposition velocities were 0.330 cm s⁻¹ for unattached ²²⁰Rn progeny and 0.0011 cm s⁻¹ for aerosol-attached ²²⁰Rn progeny using Lai-Nazaroff formulae. These deposition velocities were in the same range with the results reported in the literature. It was also found that the exposure experiments showed little influence of vertical profiles and surface orientations of the passive detector in the chamber on the detection responses, which was in good agreement with that in the model estimates. Furthermore, it was inferred that the main uncertainty of the passive detector was inhomogeneous deposition of Rn progeny onto its detection surfaces.
authors.affiliation: *Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan; †Present address: Fukushima Medical University, 1 Hikarigaoka, Fukushima 960-1295, Japan; ‡National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors.forename: Atsuyuki
authors.initials: A
authors.lastname: Sorimachi
authors.forename: Shinji
authors.initials: S
authors.lastname: Tokonami
authors.forename: Chutima
authors.initials: C
authors.lastname: Kranrod
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ishikawa
mesh_terms: D000336:Aerosols; D000396:Air Pollutants, Radioactive / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis*; D000512:Alpha Particles; D011834:Radiation Monitoring / Q000379:methods; D011886:Radon / Q000032:analysis*; D017687:Radon Daughters / Q000032:analysis
chemical_list: D000336:Aerosols; D000396:Air Pollutants, Radioactive; D017687:Radon Daughters; D011886:Radon