1、Designation: C1165 12Standard Test Method forDetermining Plutonium by Controlled-Potential Coulometryin H2SO4at a Platinum Working Electrode1This standard is issued under the fixed designation C1165; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. 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 covers the determination of milligramquantities of plutonium in unirradi
3、ated uranium-plutoniummixed oxide having a U/Pu ratio range of 0.1 to 10. This testmethod is also applicable to plutonium metal, plutonium oxide,uranium-plutonium mixed carbide, various plutonium com-pounds including fluoride and chloride salts, and plutoniumsolutions.1.2 The recommended amount of p
4、lutonium for each ali-quant in the coulometric analysis is 5 to 10 mg. Precisionworsens for lower amounts of plutonium, and elapsed time ofelectrolysis becomes impractical for higher amounts of pluto-nium.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement
5、are included in thisstandard.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 practices and determine the applica-bility of regulatory limitations
6、 prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2C757 Specification for Nuclear-Grade Plutonium DioxidePowder, SinterableC758 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofNuclea
7、r-Grade Plutonium MetalC759 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofNuclear-Grade Plutonium Nitrate SolutionsC833 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsC859 Terminology Relating to Nuclear MaterialsC1009 Guide for
8、Establishing a QualityAssurance Programfor Analytical Chemistry Laboratories Within the NuclearIndustryC1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1108 Test Method for Plutonium by Controlled-PotentialCoulometryC1128 Guide for Preparation of Workin
9、g Reference Mate-rials for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC1168 Practice for Preparation and Dissolution of Pluto-nium Materials for AnalysisC1210 Guide for Establishing a
10、Measurement System Qual-ity Control Program forAnalytical Chemistry LaboratoriesWithin the Nuclear IndustryC1297 Guide for Qualification of Laboratory Analysts forthe Analysis of Nuclear Fuel Cycle Materials3. Summary of Test Method3.1 In controlled-potential coulometry, the analyte reacts atan elec
11、trode having a maintained potential that precludesreactions of as many impurity components as is feasible. In theelectrolysis, current decreases exponentially as the reactionproceeds until a selected background current is reached. Thequantity of analyte reacted is calculable by Faradays law.Detailed
12、 discussions of the theory and applications of thistechnique are presented in Refs (1)3and (2).3.2 Plutonium and many impurity element ions are initiallyreduced in a 0.5 M H2SO4electrolyte at a platinum workingelectrode (3) maintained at + 0.310 V versus a saturatedcalomel electrode (SCE). Plutonium
13、 is then oxidized to Pu(IV)at a potential of + 0.670 V. The quantity of plutonium iscalculated from the number of coulombs required for oxidationaccording to Faradays law.Q 5 *otidt5 nwF/M (1)1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct resp
14、onsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2012. Published June 2012. Originallyapproved in 1990. Last previous edition approved in 2005 as C1165 90 (2005).DOI: 10.1520/C1165-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
15、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 a list of references at the end ofthe text.1Copyright ASTM International, 100 Barr Harbor Drive
16、, PO Box C700, West Conshohocken, PA 19428-2959, United States.Rearrangement to solve for w gives:w 5 MQ/nF (2)where:w = weight of Pu(III) oxidized to Pu(IV), g,M = gram-molecular mass of plutonium (adjusted for iso-topic composition), grams/equivalent,Q = number of coulombs to oxidize Pu(III) to Pu
17、(IV),coulombs,n = number of electron change to oxidize Pu(III) toPu(IV) = 1, andF = Faraday constant, coulomb/equivalent.3.3 An electrolyte of sulfuric acid, that selectively com-plexes Pu(IV), provides very reproducible electrolysis ofPu(III) to Pu(IV). In a 0.5 M H2SO4electrolyte, the reductionpot
18、ential of + 0.310 V for conversion of Pu(IV and VI) toPu(III) and the oxidation potential of + 0.670 V for conversionof Pu(III) to Pu(IV) accounts for about 99.9 % (as calculatedfrom the Nernst equation) conversion of the total plutonium insolution. There are few interferences at the selected potent
19、ialsof the metallic impurities usually listed in specifications for fastbreeder reactor (FBR) mixed oxide fuel.Achemical calibrationof the coulometric system using the selected potentials tech-nique is necessary to correct for the less than 100 % conver-sions of Pu(III) and Pu(IV).3.4 Sulfuric acid
20、is a convenient electrolyte since it is usedfor preliminary fuming of samples to volatilize interferingcomponents (see 5.3 and 5.4). The preliminary fuming withsulfuric acid also serves to depolymerize any polymericplutonium species, which tend to be electrolytically inactive(3).4. Significance and
21、Use4.1 This test method is to be used to ascertain whether or notmaterials meet specifications for plutonium content or pluto-nium assay, or both.4.2 A chemical calibration of the coulometer is necessaryfor accurate results.5. Interferences5.1 Categories of interferences are diverse metal ions thato
22、xidize or reduce at the potential of + 0.670 V used for theoxidation of Pu(III) to Pu(IV), organic matter, anions thatcomplex plutonium, and oxygen.5.2 The major interfering metallic impurity element, ofthose usually included in specifications for FBR mixed oxidefuel, is iron (4). In the 0.5 M H2SO4
23、electrolyte, theFe(II) Fe(III) and Pu(III) Pu(IV) couples have essentiallythe same Eovalue of + 0.490 V. The iron interference, there-fore, is quantitative and is corrected based on its measuredvalue that can be determined by a spectrophotometric method(5). Alternatively, other techniques such as IC
24、P, DCP, oremission spectrometry can also be used if the iron content issufficiently low. When the iron result is 20 g/g, the lowerlimit of the spectrophotometric method, no correction isnecessary. The best available method for iron determination isrecommended since the uncertainty in the iron correc
25、tioncontributes to the uncertainty in the plutonium value.5.3 Organic matter usually is not present in calcined mixedoxide fuel pellets nor in mixed oxide powder blends preparedusing calcined uranium oxide and calcined plutonium oxide.However, it may be introduced as an impurity in reagents. Thesulf
26、uric acid fuming of reference material and of samples thatprecedes the coulometric analysis volatilizes most organiccomponents.5.4 The sulfuric acid fuming volatilizes nitrate, nitrite,fluoride, and chloride, that are introduced by the use of anitric-hydrofluoric acid mixture or acid mixtures contai
27、ningchloride for the dissolution of samples and interfere in thecoulometric determination of plutonium.5.5 Oxygen interferes and must be purged continuouslyfrom both the solution and atmosphere in the electrolysis cellwith an oxygen-free inert gas before and during the electroly-sis.NOTE 1The purge
28、gas tube extends through the cell cover and ispositioned approximately 1 cm above the sample solution in the cell. Theinert gas flow is maintained at a flow rate that causes a dimple to be seenon the surface of the solution with the stirrer off. The inert gas flow rateshould be such that no splashin
29、g occurs.5.6 Nitric acid and hydrofluoric acid must be added duringthe preparation of the plutonium metal to ensure oxidation ofthe plutonium to Pu(IV) and to match the acid matrix fromplutonium oxide dissolution. Plutonium that is dissolved inonly hydrochloric acid and then evaporated to dryness in
30、sulfuric acid while in the Pu(III) oxidation state will containtiny blue crystals within the pink plutonium (IV) sulfatematerial, and lower recoveries are experienced during thecoulometric measurement. Blue crystals are not observed whenplutonium oxide materials are dissolved in HNO3and HF acidsand
31、subsequently fumed to dryness in H2SO4.5.7 Due to a slight overlap between the potential at whichNp(VI) reduces to Np(V), +0.660 V, and the potential used inthe current method to oxidize Pu(III) to Pu(IV), +0.670 V, alarge amount of neptunium will cause the plutonium assay tobe biased high and not a
32、ccurately reflect the plutonium contentof the material being analyzed. Thus, neptunium can only betolerated up to 1 % in the sample, above that level theneptunium must be removed prior to the sample undergoing thecoulometry process.FIG. 1 Example of a Cell Design Used at Los Alamos NationalLaborator
33、y (LANL)C1165 1226. Apparatus6.1 Controlled-Potential CoulometerA potentiostat hav-ing stable potential control at approximately 200 mA and 20 Vand an integrator capable of 0.05 % reproducibility are re-quired. The linearity of the integrator should be better than0.1 % for the selected range.46.2 Ce
34、ll AssemblyA cell assembly similar to the onedescribed in Ref (5) has been used satisfactorily. Cell design isvery critical in controlled-potential coulometry. There aremany factors that must be considered in choosing or designinga cell assembly. It is beyond the scope of this test method todescribe
35、 all of the factors that should be considered. Athorough detailed discussion of electrolysis cell design ispresented in Ref (2).NOTE 2Drawing (see Fig. 1) of a cell design that has been success-fully used at the Los Alamos National Laboratory. The titration cellconsists of a 50 mL cut off beaker.6.3
36、 Timer or stopwatch for measuring electrolysis times(capable of measuring in seconds).7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents o
37、f the American Chemical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterUnless otherwise indicated, referen
38、cesto water shall be understood to mean distilled or deionizedwater.7.3 Argon, Oxygen-Free (99.99 %)Helium, nitrogen, orother pure inert gas may be used.7.4 Hydrochloric Acid (HCl, 10.9 M)Concentrated HCl,ACS ultratrace grade.7.5 Hydrochloric Acid (HCl, 6 M)Add 500 mL of con-centrated 10.9 M HCl to
39、less than 500 mL of water and diluteto 1 L with water.7.6 Hydrochloric Acid (HCl, 1.0 M)Add 82.6 mL ofconcentrated 10.9 M HCl to water and dilute to 1L.7.7 Hydrofluoric Acid (HF, 29M)Concentrated HF, ACSultratrace grade.7.8 Hydrofluoric Acid (HF, 1.3 M)Add 4.8 mL of concen-trated 29 M HF to water an
40、d dilute to 100 mL.7.9 Nitric Acid (HNO3, 15.9 M)Concentrated HNO3,ACSultratrace grade.7.10 Sulfuric Acid (H2SO4, 18.1 M)Concentrated H2SO4,ACS ultratrace grade.7.11 Sulfuric Acid (3 M)Add 168 mL of concentratedH2SO4to water, while stirring, and dilute to 1 L with water.7.12 Sulfuric Acid (0.5 M)Add
41、 28 mL of concentratedH2SO4to water, while stirring, and dilute to 1 L with water.7.13 Plutonium Reference SolutionDissolve a weighedquantity (balance capable of weighing to 0.01 mg) of 0.5 to 1 gof NBL (Note 4) CRM 126 metal (or its replacement) cleanedper certificate directions in 6 M HCl. Use a s
42、ufficient amount of6 M HCl to maintain an acid concentration of 1 to 2 M.Completely transfer the solution with 1.0 M HCl rinses to atared container, dilute to 100 to 200 g with 1.0 M HCl(to givea plutonium concentration of 5 mg/g), and weigh.NOTE 3A tared polyethylene bottle has been used successful
43、ly todispense weighed aliquants.NOTE 4To minimize measurement uncertainty, it is recommendedthat the reference and sample aliquants contain approximately the sameamount of plutonium. Users of this standard are responsible for validatingmethod performance if aliquants of standards and/or samples cont
44、ainingless than 5 mg of plutonium or greater than 10 mg of plutonium will bemeasured.New Brunswick Laboratory (NBL) Certified Reference Materials Cata-log (U.S. Department of Energy), http:/www.nbl.doe.gov.7.13.1 Dispense weighed 1 to 2 g aliquants, each containingaccurately known 5 to 10 mg quantit
45、ies of plutonium, toindividual electrolysis cells or vials for subsequent use inchemical calibration.7.13.2 Prior to using, add 0.5 mL of 3 M H2SO4, 1 drop of1.3 M HF and 1 drop of concentrated 15.9 M HNO3and fumeto dryness.7.13.3 After cooling, redissolve using a minimal amount of0.5 M H2SO4and aga
46、in fume to dryness.7.13.4 Repeat 7.13.3.8. Safety Precautions8.1 Committee C-26 Safeguards Statement6:8.1.1 The materials (nuclear grade plutonium metal, pluto-nium oxide powder, plutonium nitrate solutions, and mixedoxide and carbide powders and pellets) to which this testmethod applies, are subjec
47、t to nuclear safeguards regulationsgoverning their possession and use. This test method has beendesignated as technically acceptable for generating safeguardsaccountability measurement data.8.1.2 When used in conjunction with appropriate certifiedreference materials (CRMs), this test method can demo
48、nstratetraceability to the national measurements base. However,adherence to this test method does not automatically guaranteeregulatory acceptance of the resulting safeguards measure-ments. It remains the sole responsibility of the user of this testmethod to ensure that its application to safeguards
49、 has theapproval of the proper regulatory authorities.8.2 WarningHydrofluoric acid is a highly corrosive acidthat can severely burn skin, eyes, and mucous membranes.4Coulometer suppliers or designers who have reported instrument performancesthat are consistent with the specification provided in this standard include: the SRNLCoulometer, Savannah River National Laboratory,Aiken, South Carolina, USA; theMayak Coulometer PIK-200, Ozersk, Russia; and the coulometer at the LAMMLaboratory, CEA Centre de Marcoule, Bagnols-sur-CreCedex, France. If you areaware o
