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액체섬광계수기를 이용한 지하수 내 우라늄 동위원소 측정법에 관한 연구

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

  • 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))
  • 투고 : 2012.03.21
  • 심사 : 2012.04.09
  • 발행 : 2012.04.25

초록

액체섬광계수기를 이용한 지하수 내 우라늄 동위원소의 최적 측정방법에 대한 연구를 수행하였다. 용매추출법을 이용해 우라늄을 추출하였고, 시료량과 pH에 따른 추출효율을 조사하였다. 우라늄 추출효율에 미치는 영향을 조사하기 위해 표준용액을 사용하여 100 mL~1 L 범위에서 시료량을 변화 시켰으며 pH는 0.5~10 범위에서 측정하였다. 실험결과 우라늄의 추출효율은 pH에 매우 민감한 것으로 나타났으며 pH 2 에서 최고치를 나타냈다. 이에 반해 시료량은 추출효율에 큰 영향을 미치지 않는 것으로 나타났다. 우라늄 표준시료를 이용한 실험 결과 추출효율은 $95.93{\pm}0.77%$ 이었고, 계측시간 5시간을 기준으로 한 우라늄의 검출한계는 0.018 Bq/L 이었다. 본 연구결과로부터 지하수에 함유된 우라늄의 최적추출 및 측정법을 확립할 수 있었고 본 방법의 검증을 위해서 지하수 중 우라늄의 분석에 일반적으로 사용되는 ICP-MS 측정결과와의 비교분석도 함께 수행하였다. 본 연구에서 개발된 분석법을 대전 주변 지역 네 곳의 지하수를 대상으로 우라늄 함량 및 동위원소 비의 측정에 적용한 결과 우라늄의 농도는 0.59~6.69 Bq/L 그리고 $^{234}U/^{238}U$의 방사성 비는 0.88~1.40 범위로 나타내었다.

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.

키워드

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