1.1 本试验方法描述了使用层析γ扫描（TGS）对容器内发射γ射线的放射性核素进行无损检测（NDA）。高分辨率伽马射线光谱学用于检测和量化相关放射性核素。外部伽马射线传输源的衰减用于校正放射性核素发射伽马射线的测量，以实现项目中放射性核素的定量测定。 1.2 试验方法涵盖的TGS技术可用于在1至500升体积范围内测定罐或桶中的废料或废料。 也可以对其他项目进行分析。 1.3 测试方法将涵盖TGS程序的两种实现: (1) 同位素特定校准，使用已知放射性核素质量（或放射性）的标准来确定质量（或放射性）与校正计数率校准中的系统响应，该校准仅适用于其校准的特定放射性核素，以及 (2) 响应曲线校准，使用伽马射线标准确定系统响应作为伽马射线能量的函数，从而建立所有相关伽马发射放射性核素的校准。 1.4 该测试方法还将包括一种技术，用于将校准范围扩展到测量校准数据的极值之上和之下。 1.5 测试方法涵盖的分析技术适用于各种项目尺寸和各种基质衰减。基质衰减是基质成分、光子能量和基质密度的函数。可以分析的基质类型包括轻可燃物、水泥污泥或混凝土。它特别适用于具有异质基质材料和非晶态材料的物品- 放射性同位素分布均匀。测量的传输值应可用于允许有效的衰减校正，但不需要对容器中的所有体积元素进行校正，例如，如果插值是合理的。 1.6 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。 1.7 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。 1.8 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 TGS提供了一种非破坏性方法，可以逐个体素映射项目的衰减特性和放射性核素含量分布。通常在TGS分析中，项目的垂直层（或段）将被划分为多个体素。 相比之下，分段伽马扫描仪（SGS）只能逐段确定基质衰减和放射性核素浓度。 5.2 它已成功用于量化 238 聚氨基甲酸酯， 239 Pu，和 235 U、 0.5 g至200 g的SNM负载 239 聚氨基甲酸酯 ( 5. , 6. ) ，从1克到25克 235 U ( 7. ) ，以及从0.1 g到1 g的 238 Pu已成功测量。TGS技术也已应用于核电站产生的放射性废物的分析。核电站的放射性废物主要是活化产物（例如， 54 Mn， 58 有限公司， 60 有限公司， 110米 Ag）和裂变产物（例如， 137 反恐精英， 134 Cs）。核电站废物中测得的放射性核素活度范围为3.7E+04Bq至1.0E+07Bq。TGS应用于非SNM放射性核素的一些结果可以在文献中找到 ( 8. ) . 5.3 TGS技术非常适合于分析具有异质基质且包含不均匀放射性核素分布的项目。 5.4 由于分析结果是在逐个体素的基础上获得的，因此与其他伽马射线技术（如SGS）相比，TGS技术在许多情况下可以产生更精确的结果。 5.5 在确定项目内的放射性核素分布时，TGS分析明确考虑了项目不同垂直层之间的串扰。 5.6 TGS分析技术使用材料基集方法，不需要用户事先选择质量衰减曲线，前提是传输源至少有2条跨越感兴趣能量范围的伽马线。 5.7 商用TGS系统由构建块组成，可以轻松配置为在SGS模式或far模式下操作系统- 现场几何形状。 5.8 TGS提供了项目内伽马射线衰减和放射性核素浓度的三维地图，可作为诊断工具。 5.9 物品准备仅限于避免大量严重衰减材料（如铅屏蔽），以允许通过容器和基质进行充分传输。

1.1 This test method describes the nondestructive assay (NDA) of gamma ray emitting radionuclides inside containers using tomographic gamma scanning (TGS). High resolution gamma ray spectroscopy is used to detect and quantify the radionuclides of interest. The attenuation of an external gamma ray transmission source is used to correct the measurement of the emission gamma rays from radionuclides to arrive at a quantitative determination of the radionuclides present in the item. 1.2 The TGS technique covered by the test method may be used to assay scrap or waste material in cans or drums in the 1 to 500 litre volume range. Other items may be assayed as well. 1.3 The test method will cover two implementations of the TGS procedure: (1) Isotope Specific Calibration that uses standards of known radionuclide masses (or activities) to determine system response in a mass (or activity) versus corrected count rate calibration, that applies to only those specific radionuclides for which it is calibrated, and (2) Response Curve Calibration that uses gamma ray standards to determine system response as a function of gamma ray energy and thereby establishes calibration for all gamma emitting radionuclides of interest. 1.4 This test method will also include a technique to extend the range of calibration above and below the extremes of the measured calibration data. 1.5 The assay technique covered by the test method is applicable to a wide range of item sizes, and for a wide range of matrix attenuation. The matrix attenuation is a function of the matrix composition, photon energy, and the matrix density. The matrix types that can be assayed range from light combustibles to cemented sludge or concrete. It is particularly well suited for items that have heterogeneous matrix material and non-uniform radioisotope distributions. Measured transmission values should be available to permit valid attenuation corrections, but are not needed for all volume elements in the container, for example, if interpolation is justified. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 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. 1.8 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 TGS provides a nondestructive means of mapping the attenuation characteristics and the distribution of the radionuclide content of items on a voxel by voxel basis. Typically in a TGS analysis a vertical layer (or segment) of an item will be divided into a number of voxels. By comparison, a segmented gamma scanner (SGS) can determine matrix attenuation and radionuclide concentrations only on a segment by segment basis. 5.2 It has been successfully used to quantify 238 Pu, 239 Pu, and 235 U. SNM loadings from 0.5 g to 200 g of 239 Pu ( 5 , 6 ) , from 1 g to 25 g of 235 U ( 7 ) , and from 0.1 to 1 g of 238 Pu have been successfully measured. The TGS technique has also been applied to assaying radioactive waste generated by nuclear power plants (NPP). Radioactive waste from NPP is dominated by activation products (for example, 54 Mn, 58 Co, 60 Co, 110m Ag) and fission products (for example, 137 Cs, 134 Cs). The radionuclide activities measured in NPP waste is in the range from 3.7E+04 Bq to 1.0E+07 Bq. Some results of TGS application to non-SNM radionuclides can be found in the literature ( 8 ) . 5.3 The TGS technique is well suited for assaying items that have heterogeneous matrices and that contain a non-uniform radionuclide distribution. 5.4 Since the analysis results are obtained on a voxel by voxel basis, the TGS technique can in many situations yield more accurate results when compared to other gamma ray techniques such as SGS. 5.5 In determining the radionuclide distribution inside an item, the TGS analysis explicitly takes into account the cross talk between various vertical layers of the item. 5.6 The TGS analysis technique uses a material basis set method that does not require the user to select a mass attenuation curve apriori, provided the transmission source has at least 2 gamma lines that span the energy range of interest. 5.7 A commercially available TGS system consists of building blocks that can easily be configured to operate the system in the SGS mode or in a far-field geometry. 5.8 The TGS provides 3-dimensional maps of gamma ray attenuation and radionuclide concentration within an item that can be used as a diagnostic tool. 5.9 Item preparation is limited to avoiding large quantities of heavily attenuating materials (such as lead shielding) in order to allow sufficient transmission through the container and the matrix.