1.1 本指南介绍了被动伽马射线测量系统模型的使用。基于物理原理的数学模型可用于协助校准γ射线测量系统和分析测量数据。一些无损检测（NDA）测量程序涉及多种项目几何形状和矩阵组合的检测，而物理标准的制定并不可行。在这些情况下，建模可以提供一种经济高效的方法来满足用户的数据质量目标。 1.2 本标准的用户需要对辐射源和探测器、校准程序、几何形状和误差分析有科学的了解。本指南假设用户至少对这些原则和良好NDA实践有基本了解（见指南 C1592/C1592M )，如指南中NDA专业人士所定义 C1490 . 本标准的用户必须至少对用于建模的软件有基本了解。使用此类软件的说明或进一步培训不在本标准的范围内。 1.3 本指南的重点是使用高纯度锗（HPGe）探测器系统的响应模型对物品进行被动伽马射线分析。本指南中描述的许多模型也可应用于具有不同分辨率的探测器的使用，例如碘化钠或卤化镧。在这种情况下，保密协议专业人士应确定本指南各节对具体应用的适用性。 1.4 本指南中讨论的技术适用于建模各种放射性材料，包括污染场、墙壁、容器和工艺设备。 1.5 本指南无意讨论“无限平面”现场测量的建模。 ANSI N42.28对这一讨论进行了详细介绍。 1.6 本指南并不旨在解决如何制作或设置现场测量设备的物理问题，而只是解决如何选择用于分析现场测量数据的模型。 1.7 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致不符合标准。 1.8 以英寸-磅为单位的数值应视为标准值。括号中给出的值是到国际单位制的数学转换，仅供参考，不被视为标准值。 1.9 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 以下方法有助于证明在保障措施（特殊核材料）、库存控制、临界控制、去污和退役、废物处理、滞留和运输等领域的监管合规性。 5.2 本指南适用于容器中放射性核素的测定，其伽马射线吸收特性可以测量或估计，但没有代表性的认证标准。它可以应用于现场测量、测量站或实验室测量。 5.3 指南中描述的一些建模技术适用于测量土壤中均匀分布的脱落或天然放射性。 5.4 由于伽马射线的检测符合真实情况，实验室几何形状的源效率校准可能会出现不准确的情况。 建模可能是一个优势，因为它不受真实符合求和效应的影响。

1.1 This guide addresses the use of models with passive gamma-ray measurement systems. Mathematical models based on physical principles can be used to assist in calibration of gamma-ray measurement systems and in analysis of measurement data. Some nondestructive assay (NDA) measurement programs involve the assay of a wide variety of item geometries and matrix combinations for which the development of physical standards are not practical. In these situations, modeling may provide a cost-effective means of meeting user’s data quality objectives. 1.2 A scientific knowledge of radiation sources and detectors, calibration procedures, geometry and error analysis is needed for users of this standard. This guide assumes that the user has, at a minimum, a basic understanding of these principles and good NDA practices (see Guide C1592/C1592M ), as defined for an NDA professional in Guide C1490 . The user of this standard must have at least a basic understanding of the software used for modeling. Instructions or further training on the use of such software is beyond the scope of this standard. 1.3 The focus of this guide is the use of response models for high-purity germanium (HPGe) detector systems for the passive gamma-ray assay of items. Many of the models described in this guide may also be applied to the use of detectors with different resolutions, such as sodium iodide or lanthanum halide. In such cases, an NDA professional should determine the applicability of sections of this guide to the specific application. 1.4 Techniques discussed in this guide are applicable to modeling a variety of radioactive material including contaminated fields, walls, containers and process equipment. 1.5 This guide does not purport to discuss modeling for “infinite plane” in situ measurements. This discussion is best covered in ANSI N42.28. 1.6 This guide does not purport to address the physical concerns of how to make or set up equipment for in situ measurements but only how to select the model for which the in situ measurement data is analyzed. 1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.8 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 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 ====== 5.1 The following methods assist in demonstrating regulatory compliance in such areas as safeguards (Special Nuclear Material), inventory control, criticality control, decontamination and decommissioning, waste disposal, holdup and shipping. 5.2 This guide can apply to the assay of radionuclides in containers, whose gamma-ray absorption properties can be measured or estimated, for which representative certified standards are not available. It can be applied to in situ measurements, measurement stations, or to laboratory measurements. 5.3 Some of the modeling techniques described in the guide are suitable for the measurement of fall-out or natural radioactivity homogenously distributed in soil. 5.4 Source-based efficiency calibrations for laboratory geometries may suffer from inaccuracies due to gamma rays being detected in true coincidence. Modeling can be an advantage since it is unaffected by true coincidence summing effects.