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Mitsuru Ebihara,Naoki Shirai,Jin Kuwayama,Yosuke Toh 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.2
Very low contents (in the range of 10 9 g/g) of Ir in mantle-derived rock samples (komatiites) were nondestructively 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 platinumgroup elements. Because the INAA procedure used in this study is non-destructive and is almost freefrom spectral interference in gamma-ray spectrometry, the INAA values of Ir contents obtained in thisstudy 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 presentexperimental conditions, detection limits were estimated to be 1 pg/g, which corresponds to 0.1 pg for asample mass of 0.1 g. These levels can be even lowered by an order of magnitude, if necessary, whichcannot be achieved by ICP-MS carried out in this study.
Origin of Spherule Samples Recovered from Antarctic Ice Sheet-Terrestrial or Extraterrestrial?
Sekimoto, Shun,Kobayashi, Takayuki,Takamiya, Koichi,Ebihara, Mitsuru,Shibata, Seiichi Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.2
Thirty-eight spherules from the Antarctic ice sheet were analyzed using neutron activation analysis under two different conditions to investigate their origin. In almost all of these spherules, the contents of iron, cobalt, and manganese were determined to be 31% to 88%, 17 mg/kg to 810 mg/kg, and 0.017% to 7%, respectively. A detectable iridium content of 0.84 mg/kg was found in only one spherule, which was judged to be extraterrestrial in origin. A comparison of elemental compositions of the Antarctic spherules analyzed in this study with those of deep-sea sediment spherules and those of terrestrial materials revealed that most of the Antarctic spherules except for the sample in which iridium was detected could not be identified as extraterrestrial in origin.