1.1 本试验方法适用于铀同位素丰度的无损测定，通常 234 U 235 U 236 U、 以及 238 U、 在同位素均匀的含铀材料中使用伽马光谱法。材料通常在容器内，在不准备样品的情况下进行测量。 1.2 本试验方法适用于铀含量达到临界考虑允许的最大铀质量的项目。 1.3 铀可测量的伽马射线辐射覆盖了80以下的能量范围 keV至1000以上 keV。在大约100的能量区域发现了铀及其子体同位素的K-X射线发射 keV。该测试方法已应用于该能量范围的所有部分。 1.4 同位素丰度 236 U通常不能直接确定，因为它的低能伽马射线太弱 ( 1. ) 2. 以在正常测量条件下进行检测。同位素相关技术已被用于估计其相对丰度 ( 2. ) 。 1.5 该测试方法已在常规使用中证明，其同位素量分数（原子%）为 235 U从0.2 % 至97 %. 1.6 此测试方法需要衰变平衡（160 99天 %) 之间 238 U及其24.1 d半衰期 234 女儿。如果 234 她的女儿是众所周知的。 1.7 以国际单位制表示的数值应视为标准。本标准中不包括其他计量单位。 1.8 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 1.9 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ===意义和用途====== 4.1 γ法测定铀同位素组成- 射线光谱法是一种非破坏性技术，当与其他量化单一同位素的非破坏性方法（如测试方法）一起使用时 C1133 （分段伽玛扫描）， C1221 （溶液测定）， C1455 （滞留），以及 C1718 （断层扫描伽马扫描），可以提供材料衡算和保障需求所需的铀质量的完全无损检测。此方法可与量热法一起使用（试验方法 C1458 )用于千克数量的高浓缩铀，也用于转换活动井重合计数器 ( 4. ) 测量 235 U质量与铀总质量之比。 4.2 由于伽马射线光谱测定系统通常是自动化的，因此测试方法的常规使用是快速、可靠的，并且不需要劳动密集型。 该测试方法是无损的，不需要样品制备，并且不会产生废物处理问题。 4.3 测试方法不要求将系统校准到特定的几何形状。 4.4 该测试方法假设测量项目中的所有铀具有相同的同位素分布。这通常被称为同位素同质性。 4.5 试验方法的应用不取决于被分析材料的物理或化学形式。 4.6 这个 236 U丰度不是通过这种测试方法测量的，必须通过同位素相关技术、河流平均值、历史信息或其他测量技术来估计。 4.7 给定铀项目的同位素组成是该项目的一个属性，一旦确定，可以在随后的库存测量中使用，以在测量不确定性范围内验证项目的身份。 4.8 该方法还可以测量被测物品中其他伽马辐射同位素与铀的比率，假设它们与物品中的铀具有相同的空间分布。其中一些“其他”伽马辐射同位素包括铀、铯和其他裂变产物的子同位素。 4.9 该方法可应用于两个重叠能量区域的伽马射线和x射线，这取决于测量项目的性质、其容纳量以及用于数据采集的探测器的特性。 4.9.1 60 keV至250 keV-- 该能量范围需要由平面或半平面HPGe探测器提供的良好的能量分辨率。分析方法必须能够从γ- 射线峰值形状。 4.9.2 120 keV至1010 keV-- 该能量范围通常需要以较大的同轴探测器为代表的更高效率的探测器（> 25 % 相对效率）或大型半平面探测器（> 30 mm厚）。 4.10 图1 显示了产生本分析中测量到的大多数突出伽马射线和x射线的衰变。 （A） Ref的能量和分支强度( 1. )。 （B） 括号中的不确定性是绝对的1σ值。 （C） 参考文献钚衰变数据的未加权平均值的相对值( 1. )。

1.1 This test method applies to the nondestructive determination of the isotopic abundances of uranium, typically 234 U, 235 U, 236 U, and 238 U, in isotopically homogeneous uranium-bearing materials using gamma spectrometry. The material is commonly inside a container and is measured without specimen preparation. 1.2 This test method is applicable to items containing sub-gram quantities of uranium to the maximum uranium mass allowed by criticality considerations. 1.3 Measurable gamma ray emissions from uranium cover the energy range from below 80 keV to above 1000 keV. K-X-ray emissions from the isotopes of uranium and their daughters are found in the energy region around 100 keV. This test method has been applied to all portions of this energy range. 1.4 The isotopic abundance of 236 U is usually not directly determined because its low-energy gamma rays are too weak ( 1 ) 2 to be detected under normal measurement conditions. Isotopic correlation techniques have been used to estimate its relative abundance ( 2 ) . 1.5 This test method has been demonstrated in routine use for isotopic amount fraction (atom %) of 235 U from 0.2 % to 97 %. 1.6 This test method requires decay equilibrium (160 days for 99 %) between 238 U and its 24.1 d half-life 234 Th daughter. Corrections can be made if the date of chemical separation of the 234 Th daughter is known. 1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.8 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. 1.9 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 ====== 4.1 The determination of uranium isotopic composition by gamma-ray spectrometry is a nondestructive technique and when used with other nondestructive techniques that quantify a single isotope, such as Test Methods C1133 (Segmented Gamma Scanning), C1221 (Solution Assay), C1455 (Holdup),and C1718 (Tomographic Gamma Scanning), can provide a wholly nondestructive assay of uranium mass necessary for material accountancy and safeguards needs. This method can be used with calorimetry (Test Method C1458 ) for kilogram quantities of high-enriched uranium and is also used to convert an Active-Well Coincidence Counter ( 4 ) measurement of 235 U mass to total uranium mass. 4.2 Because gamma-ray spectrometry systems are typically automated, the routine use of the test method is fast, reliable, and is not labor intensive. The test method is nondestructive, requires no sample preparation, and does not create waste disposal problems. 4.3 The test method does not require that the system be calibrated to a specific geometry. 4.4 The test method assumes that all uranium in the measured item has the same isotopic distribution. This is often termed isotopic homogeneity. 4.5 The application of the test method does not depend upon the physical or chemical form of the material being analyzed. 4.6 The 236 U abundance is not measured by this test method and must be estimated from isotopic correlation techniques, stream averages, historical information, or other measurement techniques. 4.7 The isotopic composition of a given item of uranium is an attribute of that item and, once determined, can be used in subsequent inventory measurements to verify the identity of an item within the measurement uncertainties. 4.8 The method can also measure the ratio of other gamma-emitting isotopes in the measured item to uranium assuming they have the same spatial distribution as the uranium in the item. Some of these “other” gamma-emitting isotopes include daughter isotopes of uranium, cesium, and other fission products. 4.9 The method can be applied to gamma and x rays in two overlapping energy regions, depending upon the nature of the measured item, its containment, and the characteristics of the detector used for data acquisition. 4.9.1 60 keV to 250 keV— This energy range requires good energy resolution provided by planar or semi-planar HPGe detectors. The analysis methods must be capable of deconvoluting the x-ray peak line shapes from the gamma-ray peak shapes. 4.9.2 120 keV to 1010 keV— This energy range generally requires higher efficiency detectors typified by larger coaxial detectors (> 25 % relative efficiency) or large semi-planar detectors (> 30 mm thick). 4.10 Fig. 1 shows the decays that produce most of the prominent gamma and x rays that are measured in this analysis. (A) Energies and Branching Intensities from Ref ( 1 ). (B) Uncertainties in parentheses are absolute 1σ values. (C) Relative values from unweighted mean of plutonium decay data from Ref ( 1 ).