文章基本信息

标题：放射能温泉の衛生化学的研究(第5報) : 空気中の222Rnの測定法の検討および三朝, 増富温泉地域における測定結果
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作者：池淵秀治 ; 亀谷勝昭
期刊名称：Journal of Health Science
印刷版ISSN：1344-9702
电子版ISSN：1347-5207
出版年度：1970
卷号：16
期号：3
页码：138-143
DOI：10.1248/jhs1956.16.138
出版社：The Pharmaceutical Society of Japan
摘要：A new analytical method for the determination of ²²²Rn in air was studied. The method was based on the separation and determination of daughter ²¹⁴Bi which was in radioactive equilibium with ²²²Rn and the procedure was as follows. The air was sampled in a 5 liter round-bottomed flask, then 250 ml of Bi and Pb carrier solution adjusted to pH 1.0 with nitricacid was added, and the air-borne ²¹⁴Pb and ²¹⁴Bi, the daughter products of ²²²Rn, were absorbed in this solution by standing and shaking 5-6 times. ²¹⁴Bi in the solution together with Bi carrier was extracted by shaking with 1% cupferon solution and chloroform, re-extracted with 25% sulfuric acid, and precipitated by the addition of 10% sodium sulfide solution. The precipitate was dried and radioactivity of ²¹⁴Bi was measured with a low background gas-flow counter. The radioactivity of ²²²Rn can be calculated by the equations 1 and 2 shown below. [numerical formula] Where NBi is radioactivity (dpm) of ²¹⁴Bi at the time of separation of ²¹⁴Bi from ²²²Rn, t₁ is the time (min) from the separation to the beginning of measurement, t₂ is the time (min) from the separation to the end of measurement, f is the counting efficiency of ²¹⁴Bi, and A is the total count of ²¹⁴Bi in t₂-t₁. [numerical formula] Where NRn is the radioactivity (dpm) of ²²²Rn at the time of air sampling, t is the time (days) from the sampling to the separation of ²¹⁴Bi. The sensibility of this method was 5×10^-12 Ci ²²²Rn/liter of air, so that this method would be available for the determination of ²²²Rn in air in places such as the bath room of radioactive spa where extraordinary high content of ²²²Rn is expected in air. Using the above method, determination of ²²²Rn content in air was carried out at Misasa and Masutomi spa areas where many natural radioactive fountains are distributed. The ²²²Rn concentration in outdoor air was very low in both spa areas, while the air in bath room showed high concentration of ²²²Rn in both spa areas. The mean value of ²²²Rn content in air of three bath room were 42×10^-12 Ci/liter at Misasa and 13×10^-11 Ci/liter at Masutomi. These ²²²Rn contents are 13 and 4 times higher, respectively, than 1/30 of the "maximum permissible concentration in air"for occupational exposure recommended by ICRP.