Standard Active Last Updated: Dec 27, 2016
ASTM C698-16

Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Mixed Oxides ((U, Pu)O2)

Significance and Use

4.1 Mixed oxide, a mixture of uranium and plutonium oxides, is used as a nuclear-reactor fuel in the form of pellets. The plutonium content may be up to 10 weight %, and the diluent uranium may be of any 235U enrichment. In order to be suitable for use as a nuclear fuel, the material must meet certain criteria for combined uranium and plutonium content, effective fissile content, and impurity content as described in Specification C833.

4.1.1 The material is assayed for uranium and plutonium to determine whether the plutonium content is as specified by the purchaser, and whether the material contains the minimum combined uranium and plutonium contents specified on a dry weight basis.

4.1.2 Determination of the isotopic content of the plutonium and uranium in the mixed oxide is made to establish whether the effective fissile content is in compliance with the purchaser's specifications.

4.1.3 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) as described in Practice C1233.

4.2 Fitness for Purpose of Safeguards and Nuclear Safety Applications—Methods intended for use in safeguards and nuclear safety applications shall meet the requirements specified by Guide C1068 for use in such applications.


1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade mixed oxides, (U, Pu)O2, powders and pellets to determine compliance with specifications.

1.2 The analytical procedures appear in the following order:



Uranium in the Presence of Pu by Potentiometric Titration


Plutonium by Controlled-Potential Coulometry


Plutonium by Amperometric Titration with Iron (II)


Nitrogen by Distillation Spectrophotometry Using Nessler Reagent

8 to 15

Carbon (Total) by Direct Combustion-Thermal Conductivity

16 to 26

Total Chlorine and Fluorine by Pyrohydrolysis

27 to 34

Sulfur by Distillation-Spectrophotometry

35 to 43

Moisture by the Coulometric, Electrolytic Moisture Analyzer

44 to 51

Isotopic Composition by Mass Spectrometry


Rare Earths by Copper Spark Spectroscopy

52 to 59

Trace Impurities by Carrier Distillation Spectroscopy

60 to 68

Impurities by Spark-Source Mass Spectrography

69 to 75

Total Gas in Reactor-Grade Mixed Dioxide Pellets


Tungsten by Dithiol-Spectrophotometry

76 to 84

Rare Earth Elements by Spectroscopy

85 to 88

Plutonium-238 Isotopic Abundance by Alpha Spectrometry


Americium-241 in Plutonium by Gamma-Ray Spectrometry

Uranium and Plutonium Isotopic Analysis by Mass Spectrometry

89 to 97

Oxygen-to-Metal Atom Ratio by Gravimetry

98 to 105

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.4 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (For specific safety precaution statements, see Sections 6, 13.2.5, 41.7, and 93.6.1.)

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Book of Standards Volume: 12.01
Developed by Subcommittee: C26.05
Pages: 27
DOI: 10.1520/C0698-16
ICS Code: 27.120.30