Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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High sensitivity determination of iridium contents in ultra-basic rocks by INAA with coincidence gamma-ray detection

  • Ebihara, Mitsuru (Department of Earth Sciences, Waseda University) ;
  • Shirai, Naoki (Department of Chemistry, Tokyo Metropolitan University) ;
  • Kuwayama, Jin (Department of Chemistry, Tokyo Metropolitan University) ;
  • Toh, Yosuke (Nuclear Science and Engineering Center, Japan Atomic Energy Agency)
  • Received : 2021.03.12
  • Accepted : 2021.08.06
  • Published : 2022.02.25
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Abstract

Very low contents (in the range of 10-9 g/g) of Ir in mantle-derived rock samples (komatiites) were non-destructively determined by INAA coupled with coincidence gamma-ray spectrometry using 16 Ge detectors. Aliquots of the same samples were analyzed by NiS fire-assay ICP-MS for Ir and other platinum group elements. Because the INAA procedure used in this study is non-destructive and is almost free from spectral interference in gamma-ray spectrometry, the INAA values of Ir contents obtained in this study can be highly reliable. Iridium values obtained by ICP-MS were consistent with the INAA values, implying that the ICP-MS values of Ir obtained in this study are equally reliable. Under the present experimental conditions, detection limits were estimated to be 1 pg/g, which corresponds to 0.1 pg for a sample mass of 0.1 g. These levels can be even lowered by an order of magnitude, if necessary, which cannot be achieved by ICP-MS carried out in this study.

Keywords

Acknowledgement

This study was partly supported by a Grant-in-Aid (KAKENHI; No. 15340193 to ME) from the Japan Society for the Promotion of Science. Technical supports were provided by Drs. M. Oshima, Y. Hatsukawa and Y. Oura, to whom we are deeply grateful. Komatiite samples were donated by Prof. M. Humayun, to whom we are thankful. The manuscript was greatly improved by careful and through reviews by J. Mizera, G. Sun and an anonymous reviewer, to whom our thanks go. This work was conducted under the Interorganization Atomic Energy Research Program in an academic collaborative agreement between the JAEA and the University of Tokyo.

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