ASTM C698 – 98

Designation: C 698 – 98 Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Mixed Oxides ((U, Pu)O2)1 This standard is issued under the fixed designation C 698; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. 1. Scope 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 deter- mine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Uranium by Controlled-Potential Coulometry 2 Plutonium by Controlled-Potential Coulometry 2 Plutonium by Amperometric Titration with Iron (II) 2 Nitrogen by Distillation Spectrophotometry Using Nessler Re- agent 7 to 14 Carbon (Total) by Direct Combustion-Thermal Conductivity 15 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 3 Rare Earths by Copper Spark Spectroscopy 52 to 59 Trace Impurities by Carrier Distillation Spectroscopy 60 to 69 Impurities by Spark-Source Mass Spectrography 70 to 76 Total Gas in Reactor-Grade Mixed Dioxide Pellets 77 to 84 Tungsten by Dithiol-Spectrophotometry 85 to 93 Rare Earth Elements by Spectroscopy 94 to 97 Plutonium-238 Isotopic Abundance by Alpha Spectrometry 98 to 105 Americium-241 in Plutonium by Gamma-Ray Spectrometry Uranium and Plutonium Isotopic Analysis by Mass Spectrom- etry 106 to 114 Oxygen-to-Metal Atom Ratio by Gravimetry 115 to 123 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 appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. (For specific safeguard and safety precaution statements, see Sections 11, 20, 64, and 120 and 110.6.1.) 2. Referenced Documents 2.1 ASTM Standards: C 697 Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Plutonium Dioxide Powders and Pellets4 C 833 Specification for Sintered (Uranium-Plutonium) Di- oxide Pellets4 C 852 Guide for Design Criteria for Plutonium Gloveboxes C 1009 Guide for Establishing a Quality Assurance Pro- gram for Analytical Chemistry Laboratories Within the Nuclear Industry C 1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear Industry C 1108 Test Method for Plutonium by Controlled-Potential Coulometry C 1128 Guide for Preparation of Working Reference Mate- rials for Use in the Analysis of Nuclear Fuel Cycle Materials C 1156 Guide for Establishing Calibration for a Measure- ment Method Used to Analyze Nuclear Fuel Cycle Mate- rials C 1165 Test Method for Determining Plutonium by Controlled-Potential Coulometry in H2SO 4 at a Platinum Working Electrode4 C 1168 Practice for Preparation and Dissolution of Pluto- nium Materials for Analysis C 1204 Test Method for Uranium in the Presence of Pluto- nium by Iron (II) Reduction in Phosphoric Acid Followed by Chromium (VI) Titration4 C 1206 Test Method for Plutonium by Iron (II)/Chromium (VI) Amperometric Titration4 C 1210 Guide for Establishing a Measurement System Quality Control Program for Analytical Chemistry Labo- ratories Within the Nuclear Industry C 1268 Test Method for Quantitative Determination of Americium 241 in Plutonium by Gamma-Ray Spectrom- etry C 1297 Guide for Qualification of Laboratory Analysts for the Analysis of Nuclear Fuel Cycle Materials D 1193 Specification for Reagent Water5 E 60 Practice for Photometric and Spectrophotometric Methods for Chemical Analysis of Metals6 E 115 Practices for Photographic Processing in Optical1 These test methods are under the jurisdiction of ASTM Committee C-26 on Nuclear Fuel Cycle and are the direct responsibility of Subcommittee C26.05 on Methods of Test. Current edition approved Feb. 10, 1998. Published June 1998. Originally pub- lished as C698 – 72. Last previous edition C698 – 92. 2 Discontinued as of Nov. 15, 1992. 3 Discontinued as of May 30, 1980. 4 Annual Book of ASTM Standards, Vol 12.01. 5 Annual Book of ASTM Standards, Vol 11.01. 6 Annual Book of ASTM Standards, Vol 03.05. 1 Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. NOTICE: This standard has either been superceded and replaced by a new version or discontinued. Contact ASTM International (www.astm.org) for the latest information. Emission Spectrographic Analysis6 E 116 Practice for Photographic Photometry in Spectro- chemical Analysis6 3. Significance and Use 3.1 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 Specifica- tion C 833. 3.1.1 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. 3.1.2 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 purchas- er’s specifications. 3.1.3 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). 4. Reagents 4.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Commit- tee on Analytical Reagents of the American Chemical Society, where such specifications are available.7 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination. 4.2 Purity of Water— Unless otherwise indicated, refer- ences to water shall be understood to mean reagent water conforming to Specification D 1193. 5. Safety Precautions 5.1 Since plutonium- and uranium-bearing materials are radioactive and toxic, adequate laboratory facilities, gloved boxes, fume hoods, etc., along with safe techniques must be used in handling samples containing these materials. A detailed discussion of all the precautions necessary is beyond the scope of these test methods; however, personnel who handle these materials should be familiar with such safe handling practices as are given in Guide C 852 and in Refs (1) through (3).8 5.2 Committee C-26 Safeguards Statement:9 5.2.1 The materials [nuclear grade mixed oxides (U, Pu)O 2 powders and pellets] to which these test methods apply are subject to nuclear safeguards regulations governing their pos- session and use. The following analytical procedures in these test methods have been designated as technically acceptable for generating safeguards accountability measurement data: Ura- nium by Controlled Potential Coulometry; Plutonium by Controlled-Potential Coulometry; Plutonium by Amperometric Titration with Iron(II); Plutonium-238 Isotopic Abundance by Alpha Spectrometry; and Uranium and Plutonium Isotopic Analysis by Mass Spectrometry. 5.2.2 When used in conjunction with appropriate certified reference materials (CRMs), these procedures can demonstrate traceability to the national measurements base. However, adherence to these procedures does not automatically guaran- tee regulatory acceptance of the resulting safeguards measure- ments. It remains the sole responsibility of the user of these test methods to assure that its application to safeguards has the approval of the proper regulatory authorities. 6. Sampling and Dissolution 6.1 Criteria for sampling this material are given in Specifi- cation C 833. 6.2 Samples can be dissolved using the appropriate disso- lution techniques described in Practice C 1168. URANIUM IN THE PRESENCE OF PLUTONIUM BY POTENTIOMETRIC TITRATION (This test method was discontinued in 1992 and replaced by Test Method C 1204.) PLUTONIUM BY CONTROLLED POTENTIAL COULOMETRY (This test method was discontinued in 1992 and replaced by Test Method C 1165.) PLUTONIUM BY CONTROLLED-POTENTIAL COULOMETRY (With appropriate sample preparation, controlled-potential coulometric measurement as described in Test Method C 1108 may be used for plutonium determination.) PLUTONIUM BY AMPEROMETRIC TITRATION WITH IRON(II) (This test method was discontinued in 1992 and replaced by Test Method C 1206.) NITROGEN BY DISTILLATION SPECTROPHOTOMETRY USING NESSLER REAGENT 7. Scope 7.1 This test method covers the determination of 5 to 100 µg/g of nitride nitrogen in mixtures of plutonium and uranium oxides in either pellet or powder form. 8. Summary of Test Method 8.1 The sample is dissolved in hydrochloric acid by the sealed tube test method or by phosphoric acid-hydrofluoric 7 “Reagent Chemicals, American Chemical Society Specifications,” Am. Chemi- cal Soc., Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see “Reagent Chemicals and Standards,” by Joseph Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States Pharmacopeia.” 8 The boldface numbers in parentheses refer to the list of references at the end of these test methods. 9 Based upon Committee C-26 Safeguards Matrix (C 1009, C 1068, C 1128, C 1156, C 1210, C 1297). C 698 2 NOTICE: This standard has either been superceded and replaced by a new version or discontinued. Contact ASTM International (www.astm.org) for the latest information. acid solution, after which the solution is made basic with sodium hydroxide and nitrogen is separated as ammonia by steam distillation. Nessler reagent is added to the distillate to form the yellow ammonium complex and the absorbance of the solution is measured at approximately 430 nm (4, 5). 9. Apparatus 9.1 Distillation Apparatus (see Fig. 1). 9.2 Spectrophotometer, visible-range. 10. Reagents 10.1 Ammonium Chloride (NH4Cl)—Dry the salt for 2 h at 110 to 120°C. 10.2 Boric Acid Solution (40 g/litre)—Dissolve 40 g of boric acid (H3BO 3) in 800 mL of hot water. Cool to approximately 20°C and dilute to 1 L. 10.3 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro- chloric acid (HCl). 10.4 Hydrofluoric Acid (sp gr 1.15)—Concentrated hydrof- luoric acid (HF). 10.5 Nessler Reagent— To prepare, dissolve 50 g of potas- sium iodide (KI) in a minimum of cold ammonia-free water, approximately 35 mL. Add a saturated solution of mercuric chloride (HgCl2, 22 g/350 mL) slowly until the first slight precipitate of red mercuric iodide persists. Add 400 mL of 9 N sodium hydroxide (NaOH) and dilute to 1 L with water. Mix, and allow the solution to stand overnight. Decant the superna- tant liquid and store in a brown bottle. 10.6 Nitrogen, Standard Solution (1 mL 5 0.01 mg N)— Dissolve 3.819 g of NH 4Cl in water and dilute to 1 L. Transfer 10 mL of this solution to a 1-L volumetric flask and dilute to volume with ammonia-free water. 10.7 Sodium Hydroxide (9 N)—Dissolve 360 g of sodium hydroxide (NaOH) in ammonia-free water and dilute to 1 L. 10.8 Sodium Hydroxide Solution —(50 %)—Dissolve NaOH in an equal weight of ammonia-free water. 10.9 Water, Ammonia-Free—To prepare, pass distilled wa- ter through a mixed-bed resin demineralizer and store in a tightly stoppered chemical-resistant glass bottle. 11. Precautions 11.1 The use of ammonia or other volatile nitrogenous compounds in the vicinity can lead to serious error. The following precautionary measures should be taken: (1) Clean all glassware and rinse with ammonia-free water immediately prior to use, and ( 2) avoid contamination of the atmosphere in the vicinity of the test by ammonia or other volatile nitrog- enous compounds. 12. Procedure 12.1 Dissolution of Sample: 12.1.1 Transfer a weighed sample, in the range from 1.0 to 1.5 g, to a 50-mL beaker. NOTE 1—Pellet samples should be crushed to a particle size of 1 mm or less with a diamond mortar. 12.1.2 To the sample add 5 mL of HCl (sp gr 1.19) and 3 drops of HF (sp gr 1.15). Heat to put the sample into solution. NOTE 2—Concentrated phosphoric acid or mixtures of phosphoric acid and hydrofluoric acids or of phosphoric and sulfuric acids may be used for the dissolution of mixed oxide samples. Such acids may require a purification step in order to reduce the nitrogen blank before being used in this procedure. 12.2 Distillation: 12.2.1 Quantitatively transfer the sample solution to the distilling flask of the apparatus. Add 20 mL of ammonia-free water and then clamp the flask into place on the distillation apparatus (see Fig. 2). 12.2.2 Turn on the steam generator but do not close with the stopper. 12.2.3 Add 5 mL of boric acid solution (4 %) to a 50-mL graduated flask and position this trap so that the condenser tip is below the surface of the boric acid solution. 12.2.4 Transfer 20 mL of NaOH solution (50 %) to the funnel in the distillation head. 12.2.5 When the water begins to boil in the steam generator, replace the stopper and slowly open the stopcock on the distilling flask to allow the NaOH solution to run into the sample solution. NOTE 3—The NaOH solution must be added slowly to avoid a violent reaction which may lead to loss of sample. 12.2.6 Steam distill until 25 mL of distillate has collected in the trap. 12.2.7 Remove the trap containing the distillate from the distillation apparatus, and remove the stopper from the steam generator. 12.2.8 Transfer the cooled distillate to a 50-mL volumetric flask. 12.2.9 Prepare a reagent blank solution by following steps 12.1.1 through 12.2.8. FIG. 1 Distillation Apparatus C 698 3 NOTICE: This standard has either been superceded and replaced by a new version or discontinued. Contact ASTM International (www.astm.org) for the latest information. 12.3 Measurement of Nitrogen: 12.3.1 Add 1.0 mL of Nessler reagent to each of the distillates collected in 12.2.8 and 12.2.9. Dilute to volume with ammonia-free water, mix, and let stand for 10 min. 12.3.2 Measure the absorbance of the solutions at 430 nm in a 1-cm cell. Use water as the reference. 12.4 Calibration Curve: 12.4.1 Add 0, 5, 10, 25, 100, and 150 µg of nitrogen from the nitrogen standard solution to separate distilling flasks. Then, add 5 mL of HCl and 3 drops of HF plus 20 mL of ammonia-free water to each flask. 12.4.2 Process each solution by the procedure in 12.2 through 12.3 (omit step 12.2.9). 12.4.3 Correct for the reagent blank reading and plot the absorbance of each standard against micrograms of nitrogen per 50 mL of solution. 13. Calculation 13.1 From the calibration chart, read the micrograms of nitrogen corresponding to the absorbance of the sample solu- tion. 13.2 Calculate the nitrogen content of the sample as fol- lows: N, µg/g 5 ~A – B!/W (1) where: A 5 micrograms of nitrogen from sample plus reagents, B 5 micrograms of nitrogen in blank, and W 5 grams of sample. 14. Precision and Bias 14.1 The estimated relative standard deviation for a single measurement by this test method is 20 % for 3 µg of nitrogen and 3 % for 50 to 90 µg of nitrogen. CARBON (TOTAL) BY DIRECT COMBUSTION- THERMAL CONDUCTIVITY 15. Scope 15.1 This test method covers the determination of 10 to 200 µg of residual carbon in nuclear grade mixed oxides, (U,Pu)O 2. 16. Summary of Test Method 16.1 Powdered samples are covered and mixed with an accelerator in carbon-free crucibles and burned with oxygen in an induction heating furnace. Traces of sulfur compounds and water vapor are removed from the combustion products by a purification train and the resultant carbon monoxide is con- verted to carbon dioxide. The purified carbon dioxide is trapped on a molecular sieve, eluted therefrom with a stream of helium upon application to heat to the trap, and passed through a thermal conductivity cell. The amount of carbon present, being a function of the integrated change in the current of the detector cell, is read directly from a calibrated-digital voltmeter or strip-chart recorder. 17. Interferences 17.1 There are no known interferences not eliminated by the purification system. 18. Apparatus 18.1 Commercial Combustion Apparatus, suitable for the carbon determination, is often modified to facilitate mainte- nance and operation within the glove box which is required for all work with plutonium materials. 18.2 Combustion Apparatus, 10 consisting of an induction furnace, suitable for operation at 1600°C, a catalytic furnace, a purification train, a carbon dioxide trap, thermal conductivity cell with appropriate readout equipment, and a regulated supply of oxygen and helium. 18.3 Combustion Tubes— Quartz combustion tubes with integral baffle shall be used. 18.4 Crucibles—Expendable alumina or similar refractory crucibles shall be used. The use of crucible covers is optional. Satisfactory operation with covers must be established by analysis of standards. Crucibles and covers (if used) must be ignited at a temperature of 1000°C or higher for a time sufficient to produce constant blank values. 18.5 Accelerators— Granular tin, copper, iron, and copper oxide accelerators shall be used to obtain satisfactory results. The criterion for satisfactory results is the absence of signifi- cant additional carbon release upon recombustion of the specimen. 18.6 Catalytic Furnace and Tube—This unit, which is used to ensure complete conversion of CO to CO2, consists of a tube containing copper oxide and maintained at a temperature of 300°C by a small furnace. 10 A Leco Low Carbon Analyzer, sold by Laboratory Equipment Co., St. Joseph, MI, or equivalent, has been found satisfactory for this purpose. FIG. 2 Quartz Reaction Tube C 698 4 NOTICE: This standard has either been superceded and replaced by a new version or discontinued. Contact ASTM International (www.astm.org) for the latest information. 18.7 Carbon Dioxide Purifiers—The purifiers that follow the combustion tube must remove finely divided solid metallic oxides and oxides of sulfur and selenium, dry the gases before they enter the CO2 trap, and protect the absorber from outside effects. Finely divided solid metal oxides are removed from the gases during their passage through the quartz wool. The SO2 given off by materials containing sulfur is removed by MnO2 and any water vapor is absorbed in a tube containing Mg- (ClO4)2. Hot copper oxide converts carbon monoxide to carbon dioxide. Additional components in the purification train may be required when materials containing very high amounts of sulfur or of halides are being analyzed. The materials used in the purification train must be checked frequently to ensure that their absorbing capacity has not been exhausted. 18.8 Vibratory Sample Pulverizer Apparatus, 11 capable of reducing ceramic materials to a − 100-mesh powder. A stain- less steel capsule and mixing ball must be used, in order to reduce contamination of the sample with carbon. 19. Reagents and Materials 19.1 Quartz Wool, used as a dust trap at the top of the combustion tube. 19.2 Sulfuric Acid (H2SO 4, sp gr 1.84), used in the oxygen purificatio