1.1 本试验方法包括测定溶液中铀和钚的浓度和同位素组成。从核材料到环境或生物测定基质等样品中提取的纯化铀或钚被装载到质谱灯丝上。同位素比值由热电离质谱测定，浓度由同位素稀释测定。 1.2 以国际单位制表示的数值应视为标准。括号中的值仅供参考。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定安全、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（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 铀和钚氧化物可以作为芯块形式的核反应堆燃料。为了适合用作核燃料，起始材料必须符合某些规范，如规范中的规定 C757 , C833 , C753 , C776 , C1008 ，或由买方指定。铀浓度、钚浓度或两者以及同位素丰度根据本试验方法通过质谱法进行测量。 5.2 放置在质谱灯丝上的分离重元素部分必须非常纯净。 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检测器，只需要几纳克。如果使用法拉第杯，则需要几微克。随着样品尺寸的减小，样品的化学纯度变得更加重要，因为样品的离子发射受到杂质的抑制。

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 from samples ranging from nuclear materials to environmental or bioassay matrices is loaded onto a mass spectrometric filament. The isotopic ratio is determined by thermal ionization mass spectrometry, 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 , C1008 , 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 heavy 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 are required. If a Faraday cup is used, a few micrograms 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.