逐项迭代法在ID-ICP-MS测定^(239)Pu不确定度合成中的应用

Application of Termwise Iteration Method in Uncertainty Combination of ^(239)Pu Determination Using ID-ICP-MS

阐述了不确定度评估中一种不确定度合成方法——逐项迭代法,即将数学模型中的中间量用单一参数代替,分别合成中间量的不确定度,逐步迭代,直至获得测量结果的总不确定度。与传统的合成方法相比,逐项迭代法运算简便、逻辑性强、可比较性好,适用于复杂数学模型中独立分量的快速合成。采用该方法对ID-ICP-MS测定239Pu的不确定度进行了合成和评估。结果表明,R239/242m(即m239/m242测量值)的不确定度及242Pu稀释剂中239Pu杂质含量的不确定度是造成分析结果不确定度的主要因素,实际测量中应尽量提高仪器的短期稳定性,选用较纯的稀释剂或准确标定稀释剂中239 Pu的含量以降低分析结果的不确定度。

Termwise iteration method,which can be used for uncertainty combination in complicated mathematical models,was described.Compared to general methods,termwise iteration method has significant advantages of simple mathematical operation,good logic and straight comparison of the component uncertainties.As an example,the uncertainty of 239 Pu determination by ID-ICP-MS was evaluated using termwise iteration method.The major contributions to the uncertainty budget come from the measurement uncertainty of R239/242 mand the uncertainty of 239 Pu concentration in 242 Pu dilution agent.Therefore,in order to reduce the uncertainty of determination,short-term stability of ID-ICP-MS should be improved and more accurate measurement of 239 Pu concentration in242 Pu dilution agent should be performed in real operation procedure.