氧化还原电位滴定法测量铀含量的不确定度评定

    Uncertainty Evaluation of Uranium Content Measurements by Redox Potential Titration Methods

    • 摘要: 精密测量含铀核材料中的铀总含量是核设施开展核材料衡算及产品质量控制工作的重要一环。本工作通过开展模拟实验和不确定度评定,比较了硫酸亚铁还原-重铬酸钾氧化电位滴定法测定铀含量的GB 11841—1989和ASTM C1267-17两个标准方法及其中三种操作步骤的细节差异。结果显示,三种步骤的总合成不确定度均低于0.1%的国际目标值水平;GB 11841—1989测量2~3 g样品步骤的不确定度最小,更适合于标准物质定值测量;在日常测量工作中,样品的称量选用GB 11841—1989测量0.20~0.25 g样品步骤更好,重铬酸钾溶液配制和滴定选用ASTM C1267-17的步骤更好。

       

      Abstract: Uranium content measurement is very important to nuclear material accounting and product quality control in nuclear bulk facilities. It needs high accuracy and precision. In this work, 3 different measurement steps from 2 analytical standards GB 11841—1989 and ASTM C1267-17, which were uranium content test methods by iron(Ⅱ) reduction followed by chromium(Ⅵ) titration, were discussed by simulated experiments and following uncertainty evaluation. The results show that, the total uncertainties of the 3 steps are all lower than 0.1%, which is the international target value of uranium content measurement by redox potential titration method. The step for 2.3 g sample of GB 11841—1989 is more suitable to sign value measurement in reference material production, because of its lowest uncertainty. In routine testing works, the step for 0.20-0.25 g sample of GB 11841—1989 is better in sample weighting, the step of ASTM C126717 is better in titration and potassium dichromate solution preparation.

       

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