Influence of Tracer Nuclide Specific Activity Variation in Its Uncertainty Range on CIEMAT/NIST Method Results

By using the double coincidence liquid scintillation counter at the National Institute of Metrology, the influence of the tracer nuclide specific activity uncertainty on the results by the CIEMAT/NIST method was further investigated through the specific activity of radioactive medical nuclide ⁹⁹Tc^m. The experimental results reveal that the obtained universal curve （curve of free parameter versus the quench indicating parameter tSIE） is sensitive to the specific activity of tracer nuclide ³H, and brings effects to the counting efficiency and specific activity of ⁹⁹Tc^m. For the case of tracer nuclide specific activity with the uncertainty of 3%, the measured specific activity of ⁹⁹Tc^m has a variation of 1%.