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An improved method for Kr analysis by liquid scintillation counting and its application to atmospheric Kr determination |
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| Authors: | Noriyuki Momoshima Fumio Inoue Jun Shimada |
| Institution: | a Radioisotope Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan b Graduate School of Science, Kyushu University, 6-10-1Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan c Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan d Research Institute for Humanity and Nature, 457-4 Motoyama Kamigamo, Kita-ku, Kyoto 603-8047, Japan |
| Abstract: | Atmospheric 85Kr concentration at Fukuoka, Japan was determined by an improved 85Kr analytical method using liquid scintillation counting (LSC). An average value of 1.54 ± 0.05 Bq m−3 was observed in 2008, which is about two times that measured in 1981 at Fukuoka, indicating a 29 mBq y−1 rate of increase as an average for these 27 years. The analytical method developed involves collecting Kr from air using activated charcoal at liquid N2 temperature and purifying it using He at dry ice temperature, followed by Kr separation by gas chromatography. An overall Kr recovery of 76.4 ± 8.1% was achieved when Kr was analyzed in 500-1000 l of air. The Kr isolated by gas chromatography was collected on silica gel in a quartz glass vial cooled to liquid N2 temperature and the activity of 85Kr was measured with a low-background LS counter. The detection limit of 85Kr activity by the present analytical method is 0.0015 Bq at a 95% confidence level, including all propagation errors, which is equivalent with 85Kr in 1.3 l of the present air under the analytical conditions of 72.1% counting efficiency, 0.1597 cps background count rate, and 76.4% Kr recovery. |
| Keywords: | Analysis Kr-85 Atmosphere Liquid scintillation counting Background level |
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