1.1 本试验方法规定了使用X射线发生器，通过结合K边吸收密度测定法（KED）和K X射线荧光法（XRF）测定硝酸溶液中铀和钚的体积浓度。它被称为“混合K边”（HKED）技术，其原始实现在参考文献中描述 ( 1. ) . 2. 该方法适用于溶解器（输入）溶液和产品溶液。本试验方法还规定了单独使用XRF测量（独立XRF模式）测定U和Pu的低浓度（<50 g/L）。在独立模式下使用XRF测量，通常测量0.2 g/L至50 g/L范围内的溶液（含或不含U），以及0.2 g/L至50 g/L范围内的溶液（含或不含U）。 1.2 本试验方法适用于以下常见使用条件: 1.2.1 乏核燃料后处理和燃料生产。 1.2.2 圆柱形小瓶或反应杯中的均质水溶液。HKED系统可以使用两个单独的样品容器，即用于KED的矩形反应杯和用于XRF的圆柱形小瓶。或者，对于K-Edge和XRF，也有使用单个圆柱形小瓶中包含的样品的HKED系统。 1.2.3 两种样品配置（用于K边缘密度测定的矩形反应杯和用于XRF的圆柱形小瓶）产生的结果符合国际目标值（ITV） ( 1. ) . 1.2.4 与双容器系统相比，单圆柱小瓶配置产生的精度结果降低。 1.2.5 该测试方法适用于不采用ITV，但有自己的数据质量目标（DQO）的设施。 1.2.6 含有铀和钚的溶液，铀浓度为150至250 g/L，铀钚比为100:1，通常存在β、γ放射性高达10 TBq/L的裂变产物。 1.2.6.1 本试验方法不适用于需要量化次要元素（如U）的样品，其中钚是主要元素。 1.2.6.2 本试验方法适用于常用过程控制应用，仅在高达10%的情况下使用XRF对5 g/L至30 g/L范围内的聚氨酯进行定量 % （~100000 ppm）的超铀杂质（主要是U和Am）。在此应用中，未量化Pu样品中的杂质浓度。 必须估计额外的不确定性，并将其纳入聚氨酯浓度结果中。 1.2.7 仅含50 g/L至400 g/L铀的溶液。 1.2.8 仅含50 g/L至400 g/L钚的溶液。 1.2.9 U和Pu浓度较低的溶液，通常在0.2 g/L至50 g/L范围内。 1.2.10 中给出的浓度范围 1.2.6 – 1.2.9 将HKED技术应用于材料控制和会计（MC&A）。对于精度要求不太严格的过程控制应用，KED方法可用于测定U或Pu浓度较低（低至30 g/L）的样品。 1.3 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 HKED技术具有高度的元素特异性，并且依赖于众所周知的受控几何体。 5.2 HKED技术可以提供溶液中锕系元素的浓度测量，其精度通常优于0.3 % 对于铀浓度>50 g/L和1 % 对于典型铀钚溶液中的钚，典型测量时间为3×1000秒（3次重复，每次1000秒有效时间） ( 1. ) . 5.3 对于纯钚产品溶液，KED技术可以实现优于0.3的测量精度 % 对于钚浓度>50 g/L，典型测量时间为3×1000 s。 5.4 对于纯铀溶液，精度优于0.3 % 当铀浓度大于50g/L时，可使用KED技术实现，典型测量时间为3×3600s。 5.5 对于浓度约为1 g/L的纯铀或纯钚溶液，使用XRF进行分析，测量精度为1。 0 % 已经实现 ( 1. ) . 对于浓度约为50 g/L的溶液，使用XRF进行分析，测量精度为0.2 % 或者更好。独立XRF分析的典型测量时间为3×3000秒。 5.6 在3×3000 s的典型测量时间内对质量控制（QC）样品进行分析。 5.7 当待测溶液的化学成分均匀时，该方法适用。 5.8 结果通常用于核燃料后处理厂的燃料制造、过程控制、质量控制、材料控制和会计以及保障措施。每个应用程序都可以有自己的数据质量目标（指南 C1068 ). 5.9 HKED仪器可使用单个圆柱形小瓶进行KED和XRF测量，或使用单独的样品容器进行KED和XRF测量。 矩形反应杯的路径长度和圆柱形小瓶的内径的典型值如所示 7.8 . 5.10 将样品转移到HKED系统中可以通过与屏蔽手套箱或热室设施连接的适当设计的样品输送系统水平完成，也可以通过气动样品转移系统垂直完成。 5.11 HKED测量的U和Pu浓度取决于样品温度。分析软件包括将室温下测得的浓度标准化为参考温度25 °C。将室温输入分析软件。HKED已被用作破坏性化学分析的快速替代品，如同位素稀释质谱（IDMS）或滴定，因为样品制备量最小，HKED的精度与此类化学分析的精度相当。 当高样本吞吐量很重要时，这尤其有用。 5.12 对于三种可能的操作模式，即仅K-Edge、混合K-Edge/XRF和独立XRF，ITV中描述了U和U/Pu样本可实现的不确定度水平，用于常规安全措施测量 ( 2. ) .

1.1 This test method specifies the determination of the volumetric uranium and plutonium concentrations, typically, in nitric acid solutions through the combination of K-Edge absorption Densitometry (KED) and K X-Ray fluorescence (XRF) using an X-Ray generator. It is known as the “Hybrid K-Edge” (HKED) technique whose original implementation is described in Ref ( 1 ) . 2 The method is applicable to dissolver (input) solutions and product solutions. The test method also specifies the determination of low concentrations (<50 g/L) of U and Pu using XRF measurements alone (the “stand-alone XRF” mode). Using the XRF measurement in the stand-alone mode, solutions in the 0.2 g/L to 50 g/L range of Pu with or without U and solutions in the 0.2 g/L to 50 g/L range of U with or without Pu are commonly measured. 1.2 This test method is applicable to the following common-use conditions: 1.2.1 Spent nuclear fuel reprocessing and fuel production. 1.2.2 Homogeneous aqueous solutions contained in cylindrical vials or cuvettes. HKED systems may use two separate sample containers, namely a rectangular cuvette for KED and a cylindrical vial for XRF. Alternatively, there are HKED systems that use a sample contained in a single cylindrical vial, for both K-Edge and XRF. 1.2.3 The results produced by the two sample configuration (a rectangular cuvette for K-Edge densitometry and a cylindrical vial for XRF) are compliant with the International Target Values (ITV) ( 1 ) . 1.2.4 The precision results produced by the single cylindrical vial configuration are degraded in comparison to the two container system. 1.2.5 This test method is applicable to facilities that do not adopt the ITVs, but have their own Data Quality Objectives (DQO). 1.2.6 Solutions which contain uranium and plutonium with uranium concentration of 150 to 250 g/L and a U:Pu ratio of 100:1 typically, in the presence of fission products with β, γ, activity of up to 10 TBq/L. 1.2.6.1 This test method is not applicable to samples where a minor element such as U needs to be quantified in which Pu is the major element. 1.2.6.2 This test method is applicable for common use process control applications for quantifying Pu in the 5 g/L to 30 g/L range using XRF only in the presence of up to ~10 % (~100 000 ppm) of transuranic impurities (predominantly U and Am). In this application, the impurity concentration in the Pu samples is not quantified. Additional uncertainties must be estimated and factored in the Pu concentration results. 1.2.7 Solutions containing 50 g/L to 400 g/L of uranium alone. 1.2.8 Solutions containing 50 g/L to 400 g/L of plutonium alone. 1.2.9 Solutions with low concentrations of U and Pu, typically in the 0.2 g/L to 50 g/L range. 1.2.10 The concentration ranges given in 1.2.6 – 1.2.9 are application of the HKED technique for Materials Control and Accountancy (MC&A) purposes. For process control applications where precision requirements are less stringent, KED method can be used to assay samples with lower concentrations of U or Pu (down to 30 g/L). 1.3 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 The HKED technique is highly element specific and depends upon a well-known controlled geometry. 5.2 The HKED technique can provide concentration measurements of actinides in solutions with precision typically better than 0.3 % for uranium concentrations >50 g/L and 1 % for plutonium in typical U-Pu solutions for a typical measurement time of 3 × 1000 s (3 replicates, 1000 s live time each) ( 1 ) . 5.3 For pure plutonium only product solutions, the KED technique can achieve measurement precisions better than 0.3 % for plutonium concentrations >50 g/L for a typical measurement time of 3 × 1000 s. 5.4 For pure uranium only solutions, precisions of better than 0.3 % can be achieved using the KED technique for uranium concentrations >50 g/L, for a typical measurement time of 3 × 3600 s. 5.5 For uranium only or plutonium only solutions of concentrations approximately 1 g/L, assayed using XRF, a measurement precision of 1.0 % has been achieved ( 1 ) . For solutions of concentration approximately 50 g/L, assayed using XRF, measurement precisions of 0.2 % or better have been achieved. The typical measurement time for stand-alone XRF assay is 3 × 3000 s. 5.6 Quality Control (QC) samples are assayed for a typical measurement time of 3 × 3000 s. 5.7 It is applicable when solutions to be measured are homogeneous with respect to chemical composition. 5.8 Results are typically used for fuel fabrication, process control, quality control, material control and accountancy, and safeguards in nuclear fuel reprocessing plants. Each application can have its own data quality objectives (Guide C1068 ). 5.9 The HKED instrument may use a single cylindrical vial for both the KED and XRF measurements, or separate sample containers for KED and XRF. The typical values for the path length of the rectangular cuvette and the inner diameter of the cylindrical vial are given in 7.8 . 5.10 The transfer of the sample into the HKED system can be accomplished either horizontally by means of a suitably designed sample conveyor system coupled to a shielded glovebox or hot cell facility or vertically through a pneumatic sample transfer system. 5.11 The U and Pu concentrations measured by HKED are dependent on the sample temperature. The analysis software includes a normalization of the measured concentration at the ambient room temperature to a reference temperature of 25 °C. The ambient room temperature is input into the analysis software. HKED has been employed as a rapid alternative to destructive chemical analyses, such as Isotope Dilution Mass Spectroscopy (IDMS) or titration, because there is minimal sample preparation, and precision of HKED is comparable to the precision of such chemical analyses. This is especially useful when high sample throughput is important. 5.12 For the three modes of operation that are possibly, namely, K-Edge only, Hybrid K-Edge/XRF, and Stand-alone XRF, the uncertainty levels that can be achieved for U and U/Pu samples have been established for routine safeguards measurements are described in the ITV ( 2 ) .