1.1 本试验方法描述了钚、氚和 241 我用的是热流量热法。对于钚，根据同位素组成，典型的适用范围对应于约0.1 g至约12kg的量，而对于氚，典型的适用范围为约0.001 g至约400g。该测试方法可适用于容器尺寸最大为380 L的材料。它通常用于测定热功率范围为0.001 W至135 W的物品。 1.2 该测试方法需要了解钚同位素的相对丰度和 241 Am/Pu质量比确定钚的总质量。 1.3 该测试方法提供了氚含量的直接测量。 1.4 该测试方法提供了一种测量 241 要么是单一同位素，要么是与钚混合。1.5 以SI单位表示的值将被视为标准值。以年表示的半衰期值也被视为标准值，其中一年等于365.25天。本标准不包括其他计量单位。 1.6 本标准并不旨在解决与其使用相关的所有安全性问题（如果有）。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法规限制的适用性。 1.7 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》中确立的国际公认的标准化原则制定的。======意义和用途====== 5.1 该测试方法可用于确定容器中存在的一种或多种同位素的数量，例如在核材料的过程监测、保障和库存中。 5.1.1 量热法被认为是测量氚的既定NDA方法。它适用于不同物理和化学形式的氚（气态、吸附态、氚化水、有机物）。 5.1.2 量热分析适用于多种含Pu固体，包括金属、合金、氧化物、氟化物、混合Pu-U氧化物、混合氧化物燃料棒、废物和废料，例如灰烬、灰烬跟、盐、坩埚和石墨碎片） ( 2 , 3 ) 自20世纪60年代中期以来，这种测试方法已在美国和欧洲设施中常规用于钚工艺测量和核材料清点 ( 2- 9 ) . 5.1.3 含Pu材料在直径范围为0.025 m至0.63 m、高度范围为0.076 m至1.38 m的量热计容器中测量。 5.2 当量热分析应用于放射性同位素混合物时，需要通过伽马射线光谱法或破坏性分析技术进行额外的非破坏性同位素分布测量，就像Pu的分析一样。 5.2.1 伽马射线光谱法通常用于确定Pu同位素组成和 241 Am与Pu比率（参见测试方法 C1030 ).然而，可以使用来自质谱和α计数测量的同位素信息来代替（参见测试方法 C697 ). 5.3 量热计测量时间范围为20分钟 ( 10 ) 适用于温度调节长达72小时的较小容器 ( 11 ) 适用于较大的容器和具有长热时间常数的物品。5.3.1 物品和物品包装的四个参数影响测量时间。这四个参数是密度、质量、热导率和温度变化。被动量热计的测量井也将影响测量时间，因为它也需要达到新的平衡温度。 5.3.2 在功率补偿模式下操作的量热计保持恒定的测量井温度，并且对测量时间没有额外的影响。 5.3.3 可以通过使用平衡预测技术、通过待测量物品的温度预处理、通过使用功率补偿技术操作量热计、或通过优化物品容器(低热质量和高热导率)和包装来减少测量时间。 5.4 物品的包装条件和基质不能改变材料的热输出，但它们通常是测量时间的决定因素，如中所述 5.3.1 . 5.4.1 无论包装条件和基质如何，容器的热量输出与其放射性同位素含量成正比，如果 (1) 该容器设计有足够厚的壁，以吸收同位素衰变沉积的全部能量——这在α和β衰变的情况下是可以预期的——并且 (2) 容器中没有其他热源。 5.4.2 该测试方法在很大程度上独立于核材料在基质中的元素分布。 5.5 热功率测量可通过用于直接校准量热计或校准二次的电气标准追溯到国际测量系统(SI) 238 聚氨酯热标准。 5.5.1 检测方法不需要代表待测材料的物理标准品。 5.5.2 热流量热法已被用于制备中子和γ射线分析系统的二级标准品 ( 7- 9 , 12- 14 ) .

1.1 This test method describes the nondestructive assay (NDA) of plutonium, tritium, and 241 Am using heat flow calorimetry. For plutonium the typical range of applicability, depending on the isotopic composition, corresponds to ~0.1 g to ~12 kg quantities while for tritium the typical range is from ~0.001 g to ~400 g. This test method can be applied to materials in a wide range of container sizes up to 380 L. It has been used routinely to assay items whose thermal power ranges from 0.001 W to 135 W. 1.2 This test method requires knowledge of the relative abundances of the plutonium isotopes and the 241 Am/Pu mass ratio to determine the total plutonium mass. 1.3 This test method provides a direct measure of tritium content. 1.4 This test method provides a measure of 241 Am either as a single isotope or mixed with plutonium. 1.5 The values stated in SI units are to be regarded as standard. Half-life values expressed in years are also regarded as standard, where one year equals 365.25 days. No other units of measurement are included in this standard. 1.6 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. 1.7 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 This test method is useful for determining the quantity of one or more isotopes present in a container like in the context of process monitoring, safeguard and inventory of nuclear materials. 5.1.1 Calorimetry is considered to be an established NDA method for the measurement of tritium. It is applied for different physical and chemical forms of tritium (gaseous, adsorbed, tritiated water, organic). 5.1.2 Calorimetry assay is applied to a wide variety of Pu-bearing solids including metals, alloys, oxides, fluorides, mixed Pu-U oxides, mixed oxide fuel pins, waste, and scrap, for example, ash, ash heels, salts, crucibles, and graphite scarfings) ( 2 , 3 ) . This test method has been routinely used at U.S. and European facilities for Pu process measurements and nuclear material accountability since the mid 1960’s ( 2- 9 ) . 5.1.3 Pu-bearing materials are measured in calorimeter containers with diameters ranging from 0.025 m to 0.63 m and heights ranging from 0.076 m to 1.38 m. 5.2 Calorimetry assay requires additional non-destructive isotopic distribution measurements by gamma-ray spectrometry or destructive analysis techniques when it is applied to blends of radioisotopes like it is the case for the assay of Pu. 5.2.1 Gamma-ray spectrometry typically is used to determine the Pu isotopic composition and 241 Am to Pu ratio (see Test Method C1030 ). However, isotopic information from mass spectrometry and alpha counting measurements may be used instead (see Test Method C697 ). 5.3 Calorimeter measurement times range from 20 min ( 10 ) for smaller, temperature-conditioned containers up to 72 h ( 11 ) for larger containers and items with long thermal time constants. 5.3.1 Four parameters of the item and the item packaging affect measurement time. These four parameters are density, mass, thermal conductivity, and change in temperature. The measurement well of passive calorimeters will also affect measurement time because it too will need to come to the new equilibrium temperature. 5.3.2 Calorimeters operated in power compensation mode maintain a constant measurement well temperature and have no additional effect on measurement time. 5.3.3 Measurement times may be reduced by using equilibrium prediction techniques, by temperature preconditioning of the item to be measured, by operating the calorimeter using the power compensation technique, or by optimization of the item container (low thermal mass and high thermal conductivity) and packaging. 5.4 The packaging conditions and matrix of the item cannot change the heat output of the material, but they are usually the determining factor for measurement time as mentioned in 5.3.1 . 5.4.1 Regardless of the packaging conditions and matrix, the heat output of a container is directly proportional to its radioisotope content if (1) the container is designed with thick enough walls to absorb the entire energy deposited by the isotope’s decay—which is to be expected in the case of alpha and beta decay—and (2) there is no other heat source in the container. 5.4.2 This test method is largely independent of the elemental distribution of the nuclear materials in the matrix. 5.5 The thermal power measurement is traceable to the international measurement systems (the SI) through electrical standards used to directly calibrate the calorimeters or to calibrate secondary 238 Pu heat standards. 5.5.1 Physical standards representative of the materials being assayed are not required for the test method. 5.5.2 Heat-flow calorimetry has been used to prepare secondary standards for neutron and gamma-ray assay systems ( 7- 9 , 12- 14 ) .