Значение и использование

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.

An assay is performed to determine whether the material has the minimum uranium content specified on a dry weight basis.

The stoichiometry of the oxide is useful for predicting its sintering behavior in the pellet production process.

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.

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).

Область применения

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 The analytical procedures appear in the following order:

Sections Uranium by Ferrous Sulfate Reduction in Phosphoric Acid and Dichromate Titration Method C1267 Test Method for Uranium By Iron (II) Reduction In Phosphoric Acid Followed By Chromium (VI) Titration In The Presence of Vanadium Uranium and Oxygen Uranium Atomic Ratio by the Ignition (Gravimetric) Impurity Correction Method C1453 Standard Test Method for the Determination of Uranium by Ignition and Oxygen to Uranium Ratio (O/U) Atomic Ratio of Nuclear Grade Uranium Dioxide Powders and Pellets Carbon (Total) by Direct Combustion-Thermal Conductivity Method C1408 Test Method for Carbon (Total) in Uranium Oxide Powders and Pellets By Direct Combustion-Infrared Detection Method Total Chlorine and Fluorine by Pyrohydrolysis Ion-Selective Electrode Method C1502 Standard Test Method for the Determination of Total Chlorine and Fluorine in Uranium Dioxide and Gadolinium Oxide     Moisture by the Coulometric, Electrolytic Moisture Analyzer Method7-14 Nitrogen by the Kjeldahl Method15-22 Isotopic Uranium Composition by Multiple-Filament Surface Ionization Mass Spectrometric Method Spectrochemical Determination of Trace Elements in High-Purity Uranium Dioxide23-30 Silver, Spectrochemical Determination of, by Gallium OxideCarrier D-C Arc Technique31 and 32 Rare Earths by Copper Spark-Spectrochemical Method Impurity Elements by a Spark-Source Mass Spectrographic Method C761 Test Method for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Uranium Hexafluoride C1287 Test Method for Determination of Impurities In Uranium Dioxide By Inductively Coupled Plasma Mass Spectrometry Surface Area by Nitrogen Absorption Method33-39 Total Gas in Reactor-Grade Uranium Dioxide Pellets Thorium and Rare Earth Elements by Spectroscopy Hydrogen by Inert Gas Fusion C1457 Standard Test Method for Determination of Total Hydrogen Content of Uranium Oxide Powders and Pellets by     Carrier Gas Extraction     Uranium Isotopic Analysis by Mass Spectrometry C1413 Test Method for Isotopic Analysis of Hydrolysed Uranium Hexafluoride and Uranyl Nitrate Solutions By Thermal Ionization Mass Spectrometry

7.1 This test method covers the determination of moisture in uranium dioxide samples. Detection limits are as low as 10 μg.

15.1 This test method covers the determination of nitride nitrogen in uranium dioxide in the range from 10 to 250 μg.

23.1 This test method covers the spectrographic analysis of nuclear-grade UO₂ for the 26 elements in the ranges indicated in Table 1.

23.2 For simultaneous determination of trace elements by plasma emission spectroscopy refer to Test Method C761.

TABLE 1 Recommended Analytical Spectral Lines and Concentration Range of Trace Elements

ElementAnalytical Line,
°A^AConcentration range, μg/g of U Ag^B 3280.68 0.1 to 50 Al 2367.06 10 to 200 As 2349.84 5 to 50 B 2497.73 0.10 to 5 Ba 4554.04 10 to 300 Be 2348.61 0.1 to 3 Bi 3067.72 5 to 50 Ca 4226.73 1 to 50 Cd 2288.02 0.15 to 5 Co 3453.51 5 to 50 Cr 2843.25 10 to 100 Cu 3247.54 1 to 10 Fe 2462.64 10 to 300 In 3256.09 5 to 50 Mg 2779.83 10 to 100 Mn 2605.69 5 to 50 Mo 3132.59 0.5 to 10 Na 3302.32 80 to 400 Ni 3050.82 5 to 100 P 2553.28 50 to 500 Pb 2833.07 5 to 50 Sb 2598.05 1 to 50 Si 2435.16 10 to 200 Sn 3175.02 5 to 50 Ti 3361.26 1 to 100 V 3183.41 1 to 100 Zn 3345.02 20 to 300 Zr 3438.23 25 to 300

^A All of the above lines are photographed in the second order, except barium and calcium which are first order lines.

^B A gallium oxide carrier must be used for silver. See Test Method E402.

31.1 This test method covers the spectrochemical determination of silver in nuclear-grade uranium dioxide. The relative standard deviation is 15 % for the concentration range of 0.1 to 50 μg/g.

33.1 This procedure is designed for a rapid determination of surface area of nuclear-grade uranium dioxide (UO₂) powders. The determination of surface area by this procedure is automatic, simple, and fast enough to be used in quality control work. The range of analysis is from 1 to 1500 m²/g.