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A study of activity ratios of uranium isotope in the groundwater using liquid scintillation counter

액체섬광계수기를 이용한 지하수 내 우라늄 동위원소 측정법에 관한 연구

  • Cho, Soo-Young (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM)) ;
  • Song, Kyung-Sun (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM)) ;
  • Lee, Kil-Yong (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM)) ;
  • Yoon, Yoon-Yeol (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM)) ;
  • Kim, Won-Baek (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM)) ;
  • Ko, Kyung-Sok (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources(KIGAM))
  • Received : 2012.03.21
  • Accepted : 2012.04.09
  • Published : 2012.04.25

Abstract

An analytical method was developed for the measurement of uranium isotope in ground water using the liquid scintillation counting technique. A LKB Wallac Quantulus 1220 liquid scintillation counter (LSC) equipped with pulse shape analyzer (PSA) and a solvent extraction method were used for the measurement of uranium isotope in ground water samples. The effect of solution volume on the extraction efficiency was evaluated for 100 to 1000 mL solutions using a NIST standard reference material (NIST SRM 4321C). The effect of groundwater pH on the extraction efficiency was also investigated for pH ranging from 0.5 to 10. It was found that the extraction efficiency had a strong dependence on pH showing a maximum at pH 2. In contrast, the effect of groundwater volume on the extraction efficiency was negligible in the range investigated. According to the method, the extraction efficiency of uranium isotopes was near 96% and the lower detection limit for uranium was 0.018 Bq/L with the counting time of 300 min. The result of this study was also verified by the conventional ICP-MS measurement. It is demonstrated that the suggested method is valuable to the determination of the optimum extraction and measurement conditions for uranium in ground water. The method was successfully applied to the ground water at four locations near the Daejeon province. It was found that the uranium content and the isotopic ratio of $^{234}U/^{238}U$ at the locations ranged 0.59~6.69 Bq/L and 0.72~1.40, respectively.

Keywords

uranium isotope;liquid scintillation counter;solvent extraction;groundwater

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