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  • 1 Department of Radiochemistry, China Institute of Atomic Energy P.O. Box 275-8, Beijing 102413, P.R. China
  • 2 Department of Radiochemistry, China Institute of Atomic Energy P.O. Box 275-8, Beijing 102413, P.R. China
  • 3 Department of Radiochemistry, China Institute of Atomic Energy P.O. Box 275-8, Beijing 102413, P.R. China
  • 4 Department of Radiochemistry, China Institute of Atomic Energy P.O. Box 275-8, Beijing 102413, P.R. China
  • 5 IsoTrace Laboratory, University of Toronto 60 St. George St., Toronto, Ontario, M5S 1A7, Canada
  • 6 IsoTrace Laboratory, University of Toronto 60 St. George St., Toronto, Ontario, M5S 1A7, Canada
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Summary  

Under an IAEA project for upgrading of reference materials, a new determination of the 129I concentration in the IAEA-375 reference material was performed. A chemical procedure was set up for the preparation of the AgI samples. Measurement of 129I was carried out using the IsoTrace Tandetron AMS facility at University of Toronto. To ensure the accuracy of the calibration, the tuning of the AMS system was iterated using not only the QC (quality control) samples but also all unknown samples. To minimize any possible current-dependent effects between 129I and 127I ions in the injection magnet, low Cs+ sputtering beam intensity (10 μA) was used. The reproducibility in determining the 129I/127I ratio in the IAEA-375 AgI samples was less than 1%. The activity concentration (CA) of 129I in the IAEA-375 reference material was determined to be 1.59±0.08 mBq . kg-1 at 95% confidence level. The present value is about 7% lower than the IAEA recommended value (1.7 mBq . kg-1) listed in 2000 or 20% lower than the recommended value (2 mBq . kg-1) listed in the IAEA AQCS Reference Material Catalogue (2002-2003). Since the IAEA recommended values for IAEA-375 materials was issued about 10 years ago and error range of the recommended values were large, the results we obtained might be useful in upgrading the recommended value.