1.1 本试验方法包括溶液中铀和钚的浓度和同位素组成的测定。将来自从核材料到环境或生物测定基质的样品的纯化铀或钚部分装载到金属丝上并放置在质谱仪中。同位素比值通过热电离质谱法测定，浓度通过同位素稀释法测定。 1.2 以SI单位表示的值应被视为标准。括号中的值仅供参考。 1.3 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安全、健康和环境实践并确定法规限制的适用性。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 铀和钚的氧化物可以以芯块的形式用作核反应堆燃料。为了适合用作核燃料，起始材料必须满足某些规格，例如在规格中找到的 C757 , C833 , C753 , C776 ，或由买方指定。铀浓度、钚浓度或两者以及同位素丰度按照该测试方法通过质谱测量。5.2 放置在质谱丝上的分离的铀或钚元素馏分必须非常纯净。所需数量取决于仪器检测系统的灵敏度。如果要使用电子倍增探测器，同位素分析只需要几纳克的U或Pu。如果使用法拉第杯，则需要数百纳克至微克的U或Pu。样品的化学纯度随着样品尺寸的减小而变得更加重要，因为样品的离子发射被杂质抑制。

1.1 This test method covers the determination of the concentration and isotopic composition of uranium and plutonium in solutions. The purified uranium or plutonium fractions from samples ranging from nuclear materials to environmental or bioassay matrices is loaded onto a metal filament and placed in the mass spectrometer. The isotopic ratio is determined by thermal ionization mass spectrometry, and the concentration is determined by isotope dilution. 1.2 The values stated in SI units are to be regarded as the standard. Values in parentheses are for information only. 1.3 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 safety, health, and environmental practices and determine the applicability of regulatory limitations 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 Uranium and plutonium oxides can be used as a nuclear-reactor fuel in the form of pellets. In order to be suitable for use as a nuclear fuel the starting material must meet certain specifications, such as found in Specifications C757 , C833 , C753 , C776 , or as specified by the purchaser. The uranium concentration, plutonium concentration, or both, and the isotopic abundances are measured by mass spectrometry following this test method. 5.2 The separated uranium or plutonium element fractions placed on mass spectrometric filaments must be very pure. The quantity required depends upon the sensitivity of the instrument detection system. If an electron multiplier detector is to be used, only a few nanograms of U or Pu are required for isotopic analysis. If a Faraday cup is used, hundreds of nanograms to micrograms of U or Pu are needed. Chemical purity of the sample becomes more important as the sample size decreases, because ion emission of the sample is suppressed by impurities.