1.1 本规程涵盖通过伽马射线光谱法测量水中发射伽马射线的放射性核素。它适用于发射能量大于45keV的伽马射线的核素。对于典型的计数系统和样本类型，活性水平约为40 Bq很容易测量，许多核素的灵敏度低至0.4Bq。由于电子限制，应避免计数率超过每秒2000次。高计数率样品可以通过稀释、增加样品到检测器的距离或使用数字信号处理器来适应。 1.2 这种做法既可用于定量测定，也可用于相对测定。在相对计数工作中，可以通过与给定核素的初始浓度（取100）进行比较来表示结果 %. 对于定量测量，结果可以用已知存在的放射性核素的已知核素标准来表示。这种做法也可以仅用于识别样本中发射伽马射线的放射性核素，而无需对其进行量化。关于放射性和辐射测量的一般信息已经公布 ( 1. ， 2. ) 。 2. 关于伽马能谱法具体应用的信息也可在文献中查阅 ( 3- 5. ) 。另请参阅中引用的ASTM标准 2.1 以及本标准末尾的相关材料部分。 1.3 本标准并不旨在解决与其使用相关的安全问题（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。 1.4 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====== 5.1 伽马射线光谱法可用于识别放射性核素和进行定量测量。半导体探测器的使用对于高分辨率测量是必要的。 5.2 样品物理几何形状的变化及其与探测器的关系将在伽马射线光谱中产生定性和定量变化。为了充分考虑这些几何效应，校准旨在复制所有条件，包括源到探测器的距离、样本形状和大小，以及测量样本时遇到的样本矩阵。 5.3 由于一些光谱分析系统是在距离检测器许多离散距离处校准的，因此可以在同一检测器上测量广泛的活性水平。对于高级样品，可以使用效率极低的几何形状。当高活性水平的样品放置在距离检测器10cm或更远的地方时，可以精确地进行定量测量。 5.4 通过将总计数率保持在每秒2000次计数以下，可以避免电子问题，如错误的死区校正、分辨率损失和随机求和 –1 )并将分析仪的死区时间保持在5以下 %. 总计数时间由样品的放射性、探测器到源的距离和可接受的泊松计数不确定度决定。

1.1 This practice covers the measurement of gamma-ray emitting radionuclides in water by means of gamma-ray spectrometry. It is applicable to nuclides emitting gamma-rays with energies greater than 45 keV. For typical counting systems and sample types, activity levels of about 40 Bq are easily measured and sensitivities as low as 0.4 Bq are found for many nuclides. Count rates in excess of 2000 counts per second should be avoided because of electronic limitations. High count rate samples can be accommodated by dilution, by increasing the sample to detector distance, or by using digital signal processors. 1.2 This practice can be used for either quantitative or relative determinations. In relative counting work, the results may be expressed by comparison with an initial concentration of a given nuclide which is taken as 100 %. For quantitative measurements, the results may be expressed in terms of known nuclidic standards for the radionuclides known to be present. This practice can also be used just for the identification of gamma-ray emitting radionuclides in a sample without quantifying them. General information on radioactivity and the measurement of radiation has been published ( 1 , 2 ) . 2 Information on specific application of gamma spectrometry is also available in the literature ( 3- 5 ) . See also the referenced ASTM Standards in 2.1 and the related material section at the end of this standard. 1.3 This standard does not purport to address 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 limitation prior to use. 1.4 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 Gamma-ray spectrometry is of use in identifying radionuclides and in making quantitative measurements. Use of a semiconductor detector is necessary for high-resolution measurements. 5.2 Variation of the physical geometry of the sample and its relationship with the detector will produce both qualitative and quantitative variations in the gamma-ray spectrum. To adequately account for these geometry effects, calibrations are designed to duplicate all conditions including source-to-detector distance, sample shape and size, and sample matrix encountered when samples are measured. 5.3 Since some spectrometry systems are calibrated at many discrete distances from the detector, a wide range of activity levels can be measured on the same detector. For high-level samples, extremely low-efficiency geometries may be used. Quantitative measurements can be made accurately and precisely when high activity level samples are placed at distances of 10 cm or more from the detector. 5.4 Electronic problems, such as erroneous deadtime correction, loss of resolution, and random summing, may be avoided by keeping the gross count rate below 2000 counts per second (s –1 ) and also keeping the deadtime of the analyzer below 5 %. Total counting time is governed by the radioactivity of the sample, the detector to source distance and the acceptable Poisson counting uncertainty.