An improved method for ⁸⁵Kr analysis by liquid scintillation counting and its application to atmospheric ⁸⁵Kr determination

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• 作者：Noriyuki Momoshima ; Fumio Inoue ; Shinji Sugihara ; Jun Shimada ; Makoto Taniguchi
• 关键词：Analysis ; Kr-85 ; Atmosphere ; Liquid scintillation counting ; Background level
• 刊名：Journal of Environmental Radioactivity
• 出版年：2010
• 出版时间：August 2010
• 年：2010
• 卷：101
• 期：8
• 页码：615-621
• 全文大小：612 K

文摘

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.