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

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

摘要: 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。

Abstract: 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%.