1、Designation: C1108 12Standard 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. A numbe
2、r 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 dis-solved plutonium from unirradiated nuclear-grade (that is,high-purity) materials by cont
3、rolled-potential coulometry.Controlled-potential coulometry may be performed in a choiceof supporting electrolytes, such as 0.9 M HNO3,1M HClO4,1M HCl, 5 M HCl, and 0.5 M H2SO4. Limitations on the use ofselected supporting electrolytes are discussed in Section 5.Optimum quantities of plutonium for t
4、his procedure are 5 to 20mg.1.2 Plutonium-bearing materials are radioactive and toxic.Adequate laboratory facilities, such as gloved boxes, fumehoods, controlled ventilation, etc., along with safe techniquesmust be used in handling specimens containing these materials.1.3 The values stated in SI uni
5、ts are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health pra
6、ctices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C859 Terminology Relating to Nuclear MaterialsC1009 Guide for Establishing and Maintaining a QualityAssurance Program forAnalytical Laboratories Within theNuclear IndustryC1068 G
7、uide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1128 Guide for Preparation of Working Reference Materi-als for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle
8、 Mate-rialsC1168 Practice for Preparation and Dissolution of PlutoniumMaterials for AnalysisC1210 Guide for Establishing a Measurement System Qual-ity Control Program for Analytical Chemistry Laborato-ries Within the Nuclear IndustryC1297 Guide for Qualification of Laboratory Analysts forthe Analysi
9、s of Nuclear Fuel Cycle MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Summary of Test Method3.1 In a controlled-potential coulometric measurement, thesubstance being determined reacts at a stationary electrode, thepotential of which is ma
10、intained at such a value that unwantedelectrode reactions are precluded under the prevailing experi-mental conditions. Those substances which have reduction-oxidation (redox) potentials near that of the ion being deter-mined constitute interferences. Electrolysis current decreasesexponentially as th
11、e reaction proceeds, until constant back-ground current is obtained. Detailed discussions of the theoryand applications of this technique have been published (1, 2, 3,4, 5, 6).3The control-potential adjustment technique (7) can beused to terminate the electrolysis of the specimen at constantbackgrou
12、nd current without exhaustive electrolysis with con-siderable reduction in operating time. Use of the control-potential adjustment technique requires that the coulometerintegrator be capable of operations in a bipolar mode and thatthe plutonium-containing solution be of high purity, that is,nuclear
13、grade.3.2 Plutonium(IV) is reduced to Pu(III) at a working elec-trode maintained at a potential more negative than the formalredox potential. Plutonium(III) is oxidized to Pu(IV) at apotential more positive than the formal redox potential. Thequantity of plutonium electrolyzed is calculated from the
14、 netnumber of coulombs required for the electrolysis, according toFaradays law. Corrections for incomplete reaction, derivedfrom the Nernst equation, must be applied for electrolysis ofthe sample aliquot (7, 8).1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and
15、 is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved July 1, 2012. Published July 2012. Originally approvedin 1988. Last previous edition approved in 2006 as C1108 99 (2006). DOI:10.1520/C1108-12.2For referenced ASTM standards, visit the ASTM website, www.a
16、stm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis test method.Copyright ASTM Internat
17、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1W 5Qs2 Qb! MnFf(1)where:W = grams of plutonium,Qs= coulombs required by the electrolysis,Qb= coulombs of background current,M = gram-atomic weight of plutonium (must be adjustedfor isotopic composition),n = nu
18、mber of electrons involved in the electrode reaction(for Pu(III) Pu(IV), n = 1),F = Faraday constant, coulombs/equivalent,4andf = fraction of plutonium electrolyzed.4. Significance and Use4.1 Factors governing selection of a method for the deter-mination of plutonium include available quantity of sa
19、mple,sample purity, desired level of reliability, and equipment.4.1.1 This test method determines 5 to 20 mg of plutoniumwith prior dissolution using Practice C1168.4.1.2 This test method calculates plutonium concentrationin solutions or mass fraction in solids using an electricalcalibration based u
20、pon Ohms Law and the Faraday Constant.4.1.3 Chemical standards are used for quality control. Whenprior chemical separation of plutonium is necessary to removeinterferences, the quality control standards should be includedwith each chemical separation batch (9).4.2 Committee C-26 Safeguards Statement
21、5:4.2.1 The materials (plutonium metal, plutonium oxide ormixed oxide (U, Pu) O2 powders and pellets) to which thistest method applies are subject to nuclear safeguards regula-tions governing their possession and use. Materials for use bythe commercial nuclear community must also meet composi-tional
22、 specifications.4.2.2 The analytical method in this test method both meetsU. S. Department of Energy guidelines for acceptability of ameasurement method for generation of safeguards accountabil-ity measurement data and also provides data that may be usedto demonstrate specification compliance in buy
23、er-seller inter-actions.5. Interferences5.1 Interference is caused by ions that are electrochemicallyactive in the range of redox potentials used or by species thatprevent attainment of 100 % current efficiency (for example,reductants, oxidants, and organic matter).5.2 PolymerPolymerized plutonium i
24、s not electrochemi-cally active (10) and thus is neither reduced nor oxidized. Thepresence of polymerized plutonium will give low results. Thepolymer may be converted to electrochemically active speciesby HF treatment (10).5.3 Pu(VI)Plutonium(VI) is only partially reduced toPu(III) in 1 M HNO3,1M HC
25、l, or 1 M HClO4supportingelectrolyte solutions; therefore, the presence of Pu(VI) can leadto inaccurate results when present even as a small fraction ofthe total plutonium. Plutonium(VI) can be completely reducedin 0.5 M H2SO4(10) or 5.5 M HCl (11) supporting electrolyte,however, quantitative reduct
26、ion has not been demonstratedwhen the control-potential adjustment technique used in thisstandard test method is applied.5.4 IronIn 0.5 M H2SO4supporting electrolyte, iron isreduced and oxidized at essentially the same formal redoxpotentials as the Pu(III)-Pu(IV) couple and thus constitutes adirect
27、interference. Iron must be removed by prior separation,or the effect of its presence must be corrected by a separatemeasurement of the iron concentration in the sample solution.In 1 M HCl, 1 M HNO3,or1M HClO4, iron interferes to alesser extent. The effect of iron in these supporting electrolytesmay
28、be minimized by the choice of redox potentials, by asecondary titration (10), or by electrochemical correction (12,13).5.5 NitritesNitrites are electrochemically active;therefore, saturated sulfamic acid solution should be added tothe electrolyte in the cell to destroy any interfering nitriteswhen a
29、 nitric acid supporting electrolyte is used.5.6 SulfateBecause of the complexing action of sulfate onPu(IV) and the resultant shift in the redox potential of thePu(III)-Pu(IV) couple, that is, the formal potential, only smallamounts of sulfate are tolerable in HNO3, HCl, and HClO4electrolytes. When
30、using these supporting electrolytes, speci-mens should be fumed to dryness to assure adequate removalof excess sulfate (see 11.3.1.3). For aliquots of dissolved MOXfuels that have not been purified by anion exchange to removethe uranium, the sulfate concentration after fuming will still beelevated.
31、A formal potential should be measured for thespecific U:Pu ratio and used in the calculations for thesealiquots.NOTE 1Interference from a sulfate concentration of 0.004 M in 1 MHClO4has been reported (10).5.7 FluorideFree fluoride cannot be tolerated and must beremoved from the specimen. Evaporation
32、 of the specimen inHNO3to a low volume and fuming with H2SO4are effective inremoving fluoride.5.8 OxygenIn H2SO4supporting electrolyte, oxygen in-terferes and must be removed. In HNO3, HCl, and HClO4supporting electrolytes, oxygen may be an interference, de-pending upon experimental conditions. Purg
33、ing the specimenwith high-purity argon prior to and during the coulometricdetermination is recommended for all electrolytes.6. Apparatus6.1 Controlled-Potential CoulometerA coulometer withthe following specifications is recommended to achieve highlyprecise and accurate results. (Room temperature sta
34、bility of61C is recommended to ensure optimum instrument perfor-mance. Instruments with smaller output current or smallervoltage span may be satisfactory.)Potentiostat (6)Output voltage 25 VOutput current 200 mA4Committee on Data for Science and Technology, CODATA, internationallyrecommended values
35、for fundamental physical constants are available at URLhttp:/physics.nist.gov/cuu/Constants/index.html.5Based upon Committee C26 Safeguards Matrix (C1009, C1068, C1128, C1156,C1210, and C1297).C1108 122Open-loop response d-c gain 105Unity-gain bandwidth 300 kHzFull-power response 10 kHz (slewing rat
36、e 0.5 V/s)Voltage zero offset stability 1-mV long termInput d-c resistance 50 MInput d-c current 10 CBias 1010.66.3 Cell AssemblyThe success of controlled-potential cou-lometric methods is strongly dependent on the design of thecell. The cell dimensions, electrode area, spacing, and stirringrate are
37、 important parameters in a design that will minimize thetime required for titration. The following components arerequired for the recommended cell assembly (Fig. 1).6.3.1 CellThe coulometry cell is fabricated from a cut-off50-mL borosilicate glass beaker with an inside diameter of 38mm and a height
38、of 42 mm; the cut edges are rounded andpolished smooth. Other cells conforming to these dimensionsare satisfactory.6.3.2 Counter Electrode and Salt Bridge TubeThe counterelectrode is a coiled length of 0.51-mm (0.020-in.) diameterplatinum wire. The salt bridge tube is unfired high-silica glass7fille
39、d with the supporting electrolyte solution.6.3.3 Reference Electrode and Salt Bridge TubeThe ref-erence electrode is a miniature saturated-calomel electrode(SCE).8The salt bridge is identical to the salt bridge describedin 6.3.2 and is also filled with supporting electrolyte solution.6.3.4 Working E
40、lectrode, fabricated from either 8Au8-5/0expanded annealed-gold metal or from 45-mesh platinumgauze (Fig. 2).6AHewlett-Packard 3455ADVM has been found to exceed these specifications.7Either a test tube with unfired Vycor bottoms of Type 7930 glass obtained fromCorning Glass Works, or a 0.5 cm long,
41、0.5-cm diameter rod of unfired Vycor Type7930 sealed into one end of a glass tube with heat-shrinkable TFE-fluorocarbontubing, has been found satisfactory for this application.8A Fisher Calomel Reference Electrode Catalog No. 13-639-79 has been foundsatisfactory.FIG. 1 Exploded View of Cell Assembly
42、: (a) Counter Electrode,(b) Cell Head, (c) Counter Electrode Frit Tube, (d) Reference Elec-trode Frit Tube, (e) NBL-Designed S-Shaped Stirrer, (f) WorkingElectrode, (g) Sample Cell, (h) Stirrer Motor, (i) Motor Pedestaland Bearing, and (j) Stirrer ShaftFIG. 2 Working Electrode (Top View)C1108 1236.3
43、.4.1 Store and condition the working electrode in accor-dance with instruction in Section 10.6.3.5 StirrerSeveral types of stirrers have performed sat-isfactorily. A paddle-type stirrer capable of being driven at1800 r/min by a synchronous motor, or a magnetically drivenstirring bar, is adequate. Ma
44、gnetic stirring slightly simplifiesthe arrangement of the cell cap. For optimum stirring efficiencywith freedom from losses due to splashing, an S-shapedpolytetrafluoroethylene stirrer (Fig. 3) (15) driven by synchro-nous motor is recommended.6.3.6 Inert Gas Inlet TubeA polyvinyl chloride tube,appro
45、ximately 3 mm in outside diameter (1 mm in insidediameter), is inserted so that its tip is about 10 mm above thesurface of the electrolyte solution. The gas flow is adjusted sothat the surface of the solution is depressed almost 3 mm. Thegas is high-purity argon. While inert gas is not required for
46、allelectrolytes, it is recommended for this procedure.6.4 Quartz Heating LampsOptimum heating or evaporat-ing efficiency without bumping of solutions, or both, isobtained using overhead heating with quartz heat lamps9controlled by a variable power supply. However, with propercare, other conventional
47、 means of heating may be used.6.5 Hot PlateRecommended for heating during the pluto-nium oxidation state adjustment with hydrogen peroxide.6.6 Quartz Clock Timer, accurate to 0.001 s.6.7 100- Precision Resistor, accurate to better than0.01 %.107. Reagents and Materials7.1 Purity of ReagentsReagent g
48、rade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.11Other grades may be used,provided it is first ascertain
49、ed that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.127.2 Argon, greater than 99.99 % purity.7.3 Hydrochloric Acid, concentrated hydrochloric acid(HCl, specific gravity 1.19).7.4 Hydrochloric Acid (1 M), prepare by diluting 85 mL ofhydrochloric acid to 1 L with water.7.5 Hydrochloric Acid-Nitric Acid-Hydrofluoric Acid Mix-ture (5.4 M HCl-1.6 M HNO3-0.014 M HF)Prepare byslowly adding 450 mL hydrochloric acid, 100 mL nitric acid,and 10 drops hydrofluoric acid to 450 mL water in a polyt
