99Tc has been widely distributed in the environment through nuclear bomb testing, the unclear fuel cycle, and nuclear medicine. In order to carry out the application of 99Tc in environment, the detection method by using AMS are now being developed in CIAE. For the sample preparation, the methods of 99Tc chemical extraction and separation of technetium and ruthenium have been explored. In order to monitor the chemical yield and check the capacity of chemical separation the radioisotopes of 95mTc and 103Ru, which were produced by the 95Mo(p,n)95mTc reaction and 102Ru(n, g)103Ru reaction respectively, were added as tracer. The Nb2O5 was used as sample matrix and AMS system normalization, but there are about 0.1ppb level of Ru in the reagent according to our AMS measurement, So a chemical procedure was also explored to remove the Ru from the reagent using 103Ru as a tracer. For the AMS measurement, the TcO- was extracted from the ion source, and the 99Tc10+ with an energy of 90MeV was selected by the high energy spectrometer. Two different method are used to separate 99Ru and 99Tc in the final detector system, one is the energy loss method, a four-anode gas ionization detector is used to separate 99Ru and 99Tc according to different energy loss, a rejection of 99Ru by up to an order of magnitude is obtained by using this method; another method is the isotope correction method, in our case, the 99Ru contribution to the mass 99 events is subtracted according to the 101Ru counts. Form measurement results of our series standard samples, We found this method working well.
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