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

作者：Momoshima Noriyuki^*; Inoue Fumio; Sugihara Shinji; Shimada Jun; Taniguchi Makoto

来源：Journal of Environmental Radioactivity, 2010, 101(8): 615-621.

DOI：10.1016/j.jenvrad.2010.03.009

• Analysis
• Kr-85
• Atmosphere
• Liquid scintillation counting
• Background level

Atmospheric Kr-85 concentration at Fukuoka, Japan was determined by an improved Kr-85 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 N-2 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 I of air. The Kr isolated by gas chromatography was collected on silica gel in a quartz glass vial cooled to liquid N-2 temperature and the activity of Kr-85 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 Kr-85 in 1.3 I of the present air under the analytical conditions of 72.1% counting efficiency, 0.1597 cps background count rate, and 76.4% Kr recovery.

• 出版日期2010-8