Preliminary Experiments Using a Passive Detector for Measuring Indoor 220Rn Progeny Concentrations with an Aerosol Chamber. Issue 6 (June 2015)

• Record Type: Journal Article
• Authors: Sorimachi, Atsuyuki; Tokonami, Shinji; Kranrod, Chutima; Ishikawa, Tetsuo
• Is Part Of: Health physics. Volume 108:Issue 6(2015:Jun.)
• Publication Date: 2015-06
• Subjects: Biophysics -- Periodicals; Health Physics -- periodicals; Radiation Protection -- periodicals; Radiotherapy -- periodicals; Medische fysica; Electronic journals; 612.01448
• DOI: 10.1097/HP.0000000000000284
• Languages: English
• ISSNs: 0017-9078

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Abstract</title> <p>This paper describes preliminary experiments using a passive detector for integrating measurements of indoor thoron (<sup>220</sup>Rn) 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 <sup>212</sup>Po due to <sup>220</sup>Rn progeny deposited on the detector surfaces. The initial experiment showed that Mylar film with area density of more than 5 mg cm<sup>−2</sup> was suitable to cut off completely alpha particles of 7.7 MeV from <sup>214</sup>Po of <sup>222</sup>Rn 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 <sup>220</sup>Rn progeny concentration. As a result of dividing deposition rates by atom concentrations, the deposition velocity was given as 0.023 cm s<sup>−1</sup> for total <sup>220</sup>Rn progeny. The model estimates of deposition velocities were 0.330 cm s<sup>−1</sup> for unattached <sup>220</sup>Rn progeny and 0.0011 cm s<sup>−1</sup> for aerosol-attached <sup>220</sup>Rn 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 <sup>220</sup>Rn progeny onto its detection surfaces.</p> </sec> </abstract>