Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 68(5): 317-329 (2019)


活性炭ラドン収集器の校正係数の導出とその有効性評価Derivation and Validity Evaluation of Calibration Factors for Activated-charcoal Radon Collectors

1神戸薬科大学放射線管理室Radioisotope Research Center, Kobe Pharmaceutical University ◇ 658–8558 兵庫県神戸市東灘区本山北町4–19–1 ◇ 4–19–1 Motoyamakitamachi, Higashinada-ku, Kobe, Hyogo 658–8558, Japan

2量子科学技術研究開発機構量子医学・医療部門高度被ばく医療センターCenter for Advanced Radiation Emergency Medicine, Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology ◇ 263–8555 千葉県千葉市稲毛区穴川4–9–1 ◇ 4–9–1 Anagawa, Inage-ku, Chiba, Chiba 263–8555, Japan

3東北大学大学院理学研究科地学専攻地圏進化学講座Department of Geoenvironmental Science, Graduate School of Science, Tohoku University ◇ 980–0845宮城県仙台市青葉区荒巻字青葉6–3 ◇ 6–3 Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi 980–8578, Japan

4滋賀医科大学実験実習支援センターCentral Research Laboratory, Shiga University of Medical Science ◇ 520–2192 滋賀県大津市瀬田月輪町 ◇ Seta Tsukinowa-cho, Otsu, Shiga 520–2192, Japan

5三重県保健環境研究所Mie Prefecture Health and Environment Research Institute ◇ 三重県四日市市桜町3684–11 ◇ 3684–11 Sakura-cho, Yokkaichi, Mie 512–1211, Japan

6神戸薬科大学薬品物理化学研究室Department of Biophysical Chemistry, Kobe Pharmaceutical University ◇ 658–8558 兵庫県神戸市東灘区本山北町4–19–1 ◇ 4–19–1 Motoyamakitamachi, Higashinada, Kobe, Hyogo 658–8558, Japan

受付日:2017年2月15日Received: February 15, 2017
受理日:2019年1月11日Accepted: January 11, 2019
発行日:2019年5月15日Published: May 15, 2019

活性炭を用いたラドン収集器(PicoRad)は,ラドンのスクリーニングに用いられてきた。しかし,米国環境保護庁は,PicoRadを含む市販のラドン収集器について適切な測定結果が得られないことを指摘した。ラドン濃度を制御した標準ラドンチャンバで,2つのロット(有効期限が異なる) PicoRadを曝露し,その標準ラドンチャンバの基準器と比較して,計数率からラドン濃度への変換式を決定した。さらに,有効性評価を行うために,PicoRadを,ラドン濃度が制御されていないラドン場で曝露し,この変換式を用いてラドン濃度を求めたところ,ラドン濃度基準値とよく一致した。この研究では,有効期限の異なるロットごとにPicoRadの変換式の係数が必要であることが明らかになった。

Radon collectors (e.g., PicoRad collectors) based on activated-charcoal have been used for screening and measuring radon. However, researchers at the U. S. Environmental Protection Agency reported that they could not verify the proper functioning of some commercially available radon detectors, including PicoRad collectors. In this study, we exposed two lots (with different expiration dates) of PicoRad collectors to the reference conditions at a controlled radon concentration within a radon chamber because the calibration factors were derived for use by a semi-empirical equation. Further, we exposed the PicoRad collectors to an uncontrolled radon atmosphere for conducting validity evaluation. The radon concentration results obtained by the PicoRad collectors using the semi-empirical equation were observed to be in good agreement with the conventional true radon concentration value. It denoted the optimal value of a quantity determined using a reference instrument. These experiments revealed that different values were required for the factors of the conversion equation of each radon collector lot with a different expiration date.

Key words: radon (222Rn); PicoRad collector; activated-charcoal radon collector; calibration factor; validity evaluation; radon chamber

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