【国外标准】 Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium Dioxide Powders and Pellets

4.1 Uranium dioxide is used as a nuclear-reactor fuel. In order to be suitable for this purpose, the material must meet certain criteria for uranium content, stoichiometry, isotopic composition, and impurity content. These test methods are designed to show whether or not a given material meets the specifications for these items as described in Specifications C753 and C776.4.1.1 An assay is performed to determine whether the material has the minimum uranium content specified on a dry weight basis.4.1.2 The stoichiometry of the oxide powder is useful for predicting its sintering behavior in the pellet production process.4.1.3 Determination of the isotopic content of the uranium in the uranium dioxide powder is made to establish whether the effective fissile content is in compliance with the purchaser's specifications.4.1.4 Impurity content is determined to ensure that the maximum concentration limit of certain impurity elements is not exceeded. Determination of impurities is also required for calculation of the equivalent boron content (EBC).4.1.5 Determination of the oxygen-to-uranium ratio is performed on the completed pellets to determine whether they have the appropriate stoichiometry for optimal performance during irradiation.1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade uranium dioxide powders and pellets to determine compliance with specifications.1.2 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.1.3 The analytical procedures appear in the following order:  Sections Uranium by Ferrous Sulfate Reduction in Phosphoric Acid and Dichromate Titration Method 2Uranium and Oxygen Uranium Atomic Ratio by the Ignition (Gravimetric) Impurity Correction Method 3Carbon (Total) by Direct Combustion-Thermal Conductivity Method 2Total Chlorine and Fluorine by Pyrohydrolysis Ion-Selective Electrode Method 3Moisture by the Coulometric, Electrolytic Moisture Analyzer Method 8 – 15Nitrogen by the Kjeldahl Method 16 – 23Isotopic Uranium Composition by Multiple-Filament Surface Ionization Mass Spectrometric Method 4Spectrochemical Determination of Trace Elements in High-Purity Uranium Dioxide 5Silver, Spectrochemical Determination of, by Gallium Oxide Carrier D-C Arc Technique 5Rare Earths by Copper Spark-Spectrochemical Method 2Impurity Elements by a Spark-Source Mass Spectrographic Method 2Surface Area by Nitrogen Absorption Method 24 – 30Total Gas in Reactor-Grade Uranium Dioxide Pellets 2Thorium and Rare Earth Elements by Spectroscopy 2Hydrogen by Inert Gas Fusion 3Uranium Isotopic Analysis by Mass Spectrometry 21.4 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.