1.1 本测试方法描述了用于无损测量 235 U或 239 钚在核设施中滞留。在处理核材料的任何设施、工艺设备、排气通风系统以及建筑物墙壁和地板中都可能发生滞留。 1.2 该测试方法包括对管理、规划、设备选择、干扰考虑、测量程序定义和资源利用有用的信息 ( 1. , 2. , 3. , 4. ) . 2. 1.3 测量工艺设备中的核材料滞留量需要对辐射源和探测器、辐射传输、校准、设施操作和不确定度分析等方面的科学知识。 它受到设施、管理、预算和时间表的限制；以及健康和安全要求。测量过程包括定义测量不确定性，并对材料的形状和分布、各种背景和干扰敏感。这项工作包括调查设施内的物质分布，可能包括潜在的大滞留表面积。管道、管道系统、手套箱和重型设备中的核材料通常以扩散和不规则的方式分布。很难定义测量几何结构，识别材料的形状，并在不受相邻辐射源干扰的情况下进行测量。 1.4 本标准并不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建立适当的安全、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《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 该测试方法的测量结果有助于证明在保障SNM库存控制、临界控制、废物处理、去污和退役（D&D）等领域的法规遵从性。本试验方法适用于测量工艺设备或可测量或估计其伽马射线吸收特性的离散项目中的滞留率。该方法可能足以准确测量放射性物质和衰减物质复杂分布的项目，但是，与放射性物质不太复杂分布的测量结果相比，测量结果具有更大的测量不确定性。 5.2 扫描- 扫描用于提供滞留范围、位置和相对数量的定性指示。它可用于计划或补充定量测量。 5.3 Nuclide映射- 核素测绘测量特定位置的持水率的相对同位素组成。它还可用于检测放射性核素的存在，这些放射性核素会发出干扰测定的辐射。核素标测最好使用高分辨率探测器（如HPGe）进行，以实现最佳核素和干扰检测。如果在测量位置的持液率不是同位素均匀的，则所测得的同位素组成将不能可靠地估计整体同位素组成。 5.4 定量测量- 这些测量结果对滞留率中所测核素的质量进行了量化。它们包括所有可用的校正（如衰减）和描述性信息（如同位素组成） 5.4.1 高质量的结果需要详细了解辐射源和探测器、辐射传输、校准、设施操作和误差分析。需要谨慎使用主题专家（指南 第490页 ). 5.5 滞留监测- 使用相同的技术和假设，定期重新测量某一特定点的滞留量，可用于检测或跟踪该点滞留量随时间的相对变化。 可以使用定性或定量方法。 5.6 间接测量- 如果两种放射性核素的丰度比已知且长期平衡（术语 第1673页 )存在。当存在干扰伽马射线或母放射性核素没有足够强的伽马射线信号以便于测量时，可以使用该方法。如果采用这种方法，必须以足够的准确度知道两种放射性核素的比率，以满足测定不确定度目标。 5.7 数学建模- 建模有助于评估复杂的测量情况。测量数据与描述设备和材料物理位置的数学模型一起使用。 ( 3. , 5. , 6. , 7. , 8. ) .

1.1 This test method describes gamma-ray methods used to nondestructively measure the quantity of 235 U or 239 Pu present as holdup in nuclear facilities. Holdup may occur in any facility where nuclear material is processed, in process equipment, in exhaust ventilation systems and in building walls and floors. 1.2 This test method includes information useful for management, planning, selection of equipment, consideration of interferences, measurement program definition, and the utilization of resources ( 1 , 2 , 3 , 4 ) . 2 1.3 The measurement of nuclear material hold up in process equipment requires a scientific knowledge of radiation sources and detectors, transmission of radiation, calibration, facility operations and uncertainty analysis. It is subject to the constraints of the facility, management, budget, and schedule; plus health and safety requirements. The measurement process includes defining measurement uncertainties and is sensitive to the form and distribution of the material, various backgrounds, and interferences. The work includes investigation of material distributions within a facility, which could include potentially large holdup surface areas. Nuclear material held up in pipes, ductwork, gloveboxes, and heavy equipment, is usually distributed in a diffuse and irregular manner. It is difficult to define the measurement geometry, to identify the form of the material, and to measure it without interference from adjacent sources of radiation. 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 Measurement results from this test method assists in demonstrating regulatory compliance in such areas as safeguards SNM inventory control, criticality control, waste disposal, and decontamination and decommissioning (D&D). This test method can apply to the measurement of holdup in process equipment or discrete items whose gamma-ray absorption properties may be measured or estimated. This method may be adequate to accurately measure items with complex distributions of radioactive and attenuating material, however, the results are subject to larger measurement uncertainties than measurements of less complex distributions of radioactive material. 5.2 Scan— A scan is used to provide a qualitative indication of the extent, location, and the relative quantity of holdup. It can be used to plan or supplement the quantitative measurements. 5.3 Nuclide Mapping— Nuclide mapping measures the relative isotopic composition of the holdup at specific locations. It can also be used to detect the presence of radionuclides that emit radiation which could interfere with the assay. Nuclide mapping is best performed using a high resolution detector (such as HPGe) for best nuclide and interference detection. If the holdup is not isotopically homogeneous at the measurement location, that measured isotopic composition will not be a reliable estimate of the bulk isotopic composition. 5.4 Quantitative Measurements— These measurements result in quantification of the mass of the measured nuclides in the holdup. They include all the corrections, such as attenuation, and descriptive information, such as isotopic composition, that are available 5.4.1 High quality results require detailed knowledge of radiation sources and detectors, transmission of radiation, calibration, facility operations and error analysis. Judicious use of subject matter experts is required (Guide C1490 ). 5.5 Holdup Monitoring— Periodic re-measurement of holdup at a defined point using the same technique and assumptions can be used to detect or track relative changes in the holdup quantity at that point over time. Either a qualitative or a quantitative method can be used. 5.6 Indirect Measurements— Quantity of a radionuclide can be determined by measurement of a daughter radionuclide or of a second radionuclide if the ratio of the abundances of the two radionuclides is known and secular equilibrium (Terminology C1673 ) is present. This can be used when there are interfering gamma rays or when the parent radionuclide does not have a sufficiently strong gamma-ray signal to be readily measured. If this method is employed, it is important that the ratio of the two radionuclides be known with sufficient accuracy to meet assay uncertainty goals. 5.7 Mathematical Modeling— Modeling is an aid in the evaluation of complex measurement situations. Measurement data are used with a mathematical model describing the physical location of equipment and materials. ( 3 , 5 , 6 , 7 , 8 ) .