示踪核素比活度在其不确定度范围内的变化对CIEMAT/NIST方法测量结果的影响

在中国计量科学研究院电离辐射研究所的双管符合液闪分析仪上，开展放射性医用核素⁹⁹Tc^m比活度的实验测量，并深入研究CIEMAT/NIST方法中由于示踪核素³H比活度自身不确定度对实验结果带来的影响。实验结果表明，液闪系统的通用曲线（自由参数随淬灭指示参数tSIE变化的曲线）对示踪核素比活度较敏感，进而会影响到被测核素⁹⁹Tc^m的探测效率和比活度测量值。对于采用扩展不确定度为3%的³H示踪核素，当其比活度在其不确定度范围内发生变化时，最终测量得到的⁹⁹Tc^m比活度有近1%的变化。

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%.