1、Designation: C1108 12C1108 17Standard Test Method forPlutonium by Controlled-Potential Coulometry1This standard is issued under the fixed designation C1108; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the determination of dissolved plutonium from unirradiated nuclear-grade (that is, high-purity)materials
3、by controlled-potential coulometry. Controlled-potential coulometry may be performed in a choice of supportingelectrolytes, such as 0.9 M HNO3, 1 M HClO4, 1 M HCl, 5 M HCl, and 0.5 M H2SO4. Limitations on the use of selected supportingelectrolytes are discussed in Section 56. Optimum quantities of p
4、lutonium for this procedure are 5 to 20 mg.1.2 Plutonium-bearing materials are radioactive and toxic. Adequate laboratory facilities, such as gloved boxes, fume hoods,controlled ventilation, etc., along with safe techniques must be used in handling specimens containing these materials.1.3 The values
5、 stated in SI units are to be regarded as the 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 responsibilityof the user of this standard to establish appropriate sa
6、fety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Deve
7、lopment of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C859 Terminology Relating to Nuclear MaterialsC1009 Guide for Establishing and Maintaining a Quality Assurance P
8、rogram for Analytical Laboratories Within the NuclearIndustryC1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear IndustryC1128 Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Cali
9、bration for a Measurement Method Used to Analyze Nuclear Fuel Cycle MaterialsC1168 Practice for Preparation and Dissolution of Plutonium Materials for AnalysisC1210 Guide for Establishing a Measurement System Quality Control Program for Analytical Chemistry Laboratories Withinthe Nuclear IndustryC12
10、97 Guide for Qualification of Laboratory Analysts for the Analysis of Nuclear Fuel Cycle MaterialsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Except as otherwise defined herein, definitions of terms are as given in Terminology C8
11、59.4. Summary of Test Method4.1 In a controlled-potential coulometric measurement, the substance being determined reacts at a stationary electrode, thepotential of which is maintained at such a value that unwanted electrode reactions are precluded under the prevailing experimentalconditions. Those s
12、ubstances which have reduction-oxidation (redox) potentials near that of the ion being determined constituteinterferences. Electrolysis current decreases exponentially as the reaction proceeds, until constant background current is obtained.1 This test method is under the jurisdiction of ASTM Committ
13、ee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.Current edition approved July 1, 2012Nov. 1, 2017. Published July 2012November 2017. Originally approved in 1988. Last previous edition approved in 20062012 asC1108 99 (2006).C1108 12. DOI: 10.152
14、0/C1108-12.10.1520/C1108-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM stan
15、dard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all case
16、s only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Detailed discussions of the theory and applications of this technique have been p
17、ublished (1, 2, 3, 4, 5, 6).3 The control-potentialadjustment technique (7) can be used to terminate the electrolysis of the specimen at constant background current withoutexhaustive electrolysis with considerable reduction in operating time. Use of the control-potential adjustment technique require
18、sthat the coulometer integrator be capable of operations in a bipolar mode and that the plutonium-containing solution be of highpurity, that is, nuclear grade.4.2 Plutonium(IV) is reduced to Pu(III) at a working electrode maintained at a potential more negative than the formal redoxpotential. Pluton
19、ium(III) is oxidized to Pu(IV) at a potential more positive than the formal redox potential. The quantity ofplutonium electrolyzed is calculated from the net number of coulombs required for the electrolysis, according to Faradays law.Corrections for incomplete reaction, derived from the Nernst equat
20、ion, must be applied for electrolysis of the sample aliquot (7,8).W 5Qs2Qb!MnFf (1)where:W = grams of plutonium,Qs = coulombs required by the electrolysis,Q b = coulombs of background current,M = gram-atomic weight of plutonium (must be adjusted for isotopic composition),n = number of electrons invo
21、lved in the electrode reaction (for Pu(III) Pu(IV), n = 1),F = Faraday constant, coulombs/equivalent,4 andf = fraction of plutonium electrolyzed.5. Significance and Use5.1 Factors governing selection of a method for the determination of plutonium include available quantity of sample, samplepurity, d
22、esired level of reliability, and equipment.5.1.1 This test method determines 5 to 20 mg of plutonium with prior dissolution using Practice C1168.5.1.2 This test method calculates plutonium concentration in solutions or mass fraction in solids using an electrical calibrationbased upon Ohms Law and th
23、e Faraday Constant.5.1.3 Chemical standards are used for quality control. When prior chemical separation of plutonium is necessary to removeinterferences, the quality control standards should be included with each chemical separation batch (9).5.2 Committee C-26 Safeguards StatementFitness for Purpo
24、se of Safeguards and: Nuclear Safety Application4.2.1 The materials (plutonium metal, plutonium oxide or mixed oxide (U, Pu) O2 powders and pellets) to which this testmethod applies are subject to nuclear safeguards regulations governing their possession and use. Materials for use by thecommercial n
25、uclear community must also meet compositional specifications. Methods intended for use in safeguards and nuclearsafety applications shall meet the requirements specified by Guide C1068 for use in such applications.4.2.2 The analytical method in this test method both meets U. S. Department of Energy
26、guidelines for acceptability of ameasurement method for generation of safeguards accountability measurement data and also provides data that may be used todemonstrate specification compliance in buyer-seller interactions.6. Interferences6.1 Interference is caused by ions that are electrochemically a
27、ctive in the range of redox potentials used or by species thatprevent attainment of 100 % current efficiency (for example, reductants, oxidants, and organic matter).6.2 PolymerPolymerized plutonium is not electrochemically active (10) and thus is neither reduced nor oxidized. Thepresence of polymeri
28、zed plutonium will give low results. The polymer may be converted to electrochemically active species byHF treatment (10).6.3 Pu(VI)Plutonium(VI) is only partially reduced to Pu(III) in 1 M HNO3, 1 M HCl, or 1 M HClO4 supporting electrolytesolutions; therefore, the presence of Pu(VI) can lead to ina
29、ccurate results when present even as a small fraction of the totalplutonium. Plutonium(VI) can be completely reduced in 0.5 M H2SO4 (10) or 5.55.5 M HCl (11) supporting electrolyte, however,quantitative reduction has not been demonstrated when the control-potential adjustment technique used in this
30、standard test methodis applied.6.4 IronIn 0.5 M H2SO4 supporting electrolyte, iron is reduced and oxidized at essentially the same formal redox potentialsas the Pu(III)-Pu(IV) couple and thus constitutes a direct interference. Iron must be removed by prior separation, or the effect ofits presence mu
31、st be corrected by a separate measurement of the iron concentration in the sample solution. In 1 M HCl, 1 M HNO3,3 The boldface numbers in parentheses refer to the list of references at the end of this test method.4 Committee on Data for Science and Technology, CODATA, internationally recommended va
32、lues for fundamental physical constants are available at URLhttp:/physics.nist.gov/cuu/Constants/index.html.C1108 172or 1 M HClO4, iron interferes to a lesser extent. The effect of iron in these supporting electrolytes may be minimized by the choiceof redox potentials, by a secondary titration (10),
33、 or by electrochemical correction (12, 13).6.5 NitritesNitrites are electrochemically active; therefore, saturated sulfamic acid solution should be added to the electrolytein the cell to destroy any interfering nitrites when a nitric acid supporting electrolyte is used.6.6 SulfateBecause of the comp
34、lexing action of sulfate on Pu(IV) and the resultant shift in the redox potential of thePu(III)-Pu(IV) couple, that is, the formal potential, only small amounts of sulfate are tolerable in HNO3, HCl, and HClO4electrolytes. When using these supporting electrolytes, specimens should be fumed to drynes
35、s to assure adequate removal of excesssulfate (see 11.3.1.312.3.1.3). For aliquots of dissolved MOX fuels that have not been purified by anion exchange to remove theuranium, the sulfate concentration after fuming will still be elevated. A formal potential should be measured for the specific U:Purati
36、o and used in the calculations for these aliquots.NOTE 1Interference from a sulfate concentration of 0.004 M in 1 M HClO4 has been reported (10).6.7 FluorideFree fluoride cannot be tolerated and must be removed from the specimen. Evaporation of the specimen in HNO3to a low volume and fuming with H2S
37、O4 are effective in removing fluoride.6.8 OxygenIn H2SO4 supporting electrolyte, oxygen interferes and must be removed. In HNO3, HCl, and HClO4 supportingelectrolytes, oxygen may be an interference, depending upon experimental conditions. Purging the specimen with high-purityargon prior to and durin
38、g the coulometric determination is recommended for all electrolytes.7. Apparatus7.1 Controlled-Potential CoulometerA coulometer with the following specifications is recommended to achieve highlyprecise and accurate results. (Room temperature stability of 61C is recommended to ensure optimum instrume
39、nt performance.Instruments with smaller output current or smaller voltage span may be satisfactory.)FIG. 1 Exploded View of Cell Assembly: (a) Counter Electrode, (b) Cell Head, (c) Counter Electrode Frit Tube, (d) Reference ElectrodeFrit Tube, (e) NBL-Designed S-Shaped Stirrer, (f) Working Electrode
40、, (g) Sample Cell, (h) Stirrer Motor, (i) Motor Pedestal and Bearing,and (j) Stirrer ShaftC1108 173Potentiostat (6)Output voltage 25 VOutput current 200 mAOpen-loop response d-c gain 105Unity-gain bandwidth 300 kHzFull-power response 10 kHz (slewing rate 0.5 V/s)Voltage zero offset stability 1-mV lo
41、ng termInput d-c resistance 50 MInput d-c current 10 CBias 1010 .57.3 Cell AssemblyThe success of controlled-potential coulometric methods is strongly dependent on the design of the cell.Thecell dimensions, electrode area, spacing, and stirring rate are important parameters in a design that will min
42、imize the time requiredfor titration. The following components are required for the recommended cell assembly (Fig. 1).7.3.1 CellThe coulometry cell is fabricated from a cut-off 50-mL borosilicate glass beaker with an inside diameter of 38 mmand a height of 42 mm; the cut edges are rounded and polis
43、hed smooth. Other cells conforming to these dimensions are satisfactory.5 A Hewlett-Packard 3455A DVM has been found to exceed these specifications.FIG. 2 Working Electrode (Top View)C1108 1747.3.2 Counter Electrode and Salt Bridge TubeThe counter electrode is a coiled length of 0.51-mm (0.020-in.)
44、diameterplatinum wire. The salt bridge tube is unfired high-silica glass6 filled with the supporting electrolyte solution.7.3.3 Reference Electrode and Salt Bridge TubeThe reference electrode is a miniature saturated-calomel electrode (SCE).7The salt bridge is identical to the salt bridge described
45、in 6.3.27.3.2 and is also filled with supporting electrolyte solution.7.3.4 Working Electrode, fabricated from either 8Au8-5/0 expanded annealed-gold metal or from 45-mesh platinum gauze (Fig.2).7.3.4.1 Store and condition the working electrode in accordance with instruction in Section 1011.7.3.5 St
46、irrerSeveral types of stirrers have performed satisfactorily.Apaddle-type stirrer capable of being driven at 1800 r/minby a synchronous motor, or a magnetically driven stirring bar, is adequate. Magnetic stirring slightly simplifies the arrangementof the cell cap. For optimum stirring efficiency wit
47、h freedom from losses due to splashing, an S-shaped polytetrafluoroethylenestirrer (Fig. 3) (15) driven by synchronous motor is recommended.7.3.6 Inert Gas Inlet TubeA polyvinyl chloride tube, approximately 3 mm in outside diameter (1 mm in inside diameter), isinserted so that its tip is about 10 mm
48、 above the surface of the electrolyte solution. The gas flow is adjusted so that the surfaceof the solution is depressed almost 3 mm. The gas is high-purity argon. While inert gas is not required for all electrolytes, it isrecommended for this procedure.7.4 Quartz Heating LampsOptimum heating or eva
49、porating efficiency without bumping of solutions, or both, is obtained usingoverhead heating with quartz heat lamps8 controlled by a variable power supply. However, with proper care, other conventionalmeans of heating may be used.7.5 Hot PlateRecommended for heating during the plutonium oxidation state adjustment with hydrogen peroxide.7.6 Quartz Clock Timer, accurate to 0.001 s.6 Either a test tube with unfired Vycor bottoms of Type 7930 glass obtained from Corning Glass Works, or a 0.5 cm long, 0.5-cm diameter rod of unfired Vycor Type 7930sea
