1、Designation: C 1165 90 (Reapproved 2005)Standard Test Method forDetermining Plutonium by Controlled-Potential Coulometryin H2SO4at a Platinum Working Electrode1This standard is issued under the fixed designation C 1165; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of milligramquantities of
3、plutonium in unirradiated 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 re
4、commended amount of plutonium 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
5、units of measurement 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 r
6、egulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2C 757 Specification for Nuclear-Grade Plutonium DioxidePowder, SinterableC 758 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radioche
7、mical Analysis ofNuclear-Grade Plutonium MetalC 759 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofNuclear-Grade Plutonium Nitrate SolutionsC 833 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsC 859 Terminology Relating to Nuclear
8、 Materials3C 1009 Guide for Establishing a Quality Assurance Pro-gram for Analytical Chemistry Laboratories Within theNuclear Industry3C 1068 Guide for Qualification of Measurement Methodsby a Laboratory Within the Nuclear IndustryC 1108 Test Method for Plutonium by Controlled-PotentialCoulometryC 1
9、128 Guide for Preparation of Working Reference Mate-rials for Use in the Analysis of Nuclear Fuel CycleMaterialsC 1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC 1168 Practice for Preparation and Dissolution of Pluto-nium Materials for
10、 AnalysisC 1210 Guide for Establishing a Measurement SystemQuality Control Program for Analytical Chemistry Labo-ratories Within the Nuclear Industry3C 1297 Guide for Qualification of Laboratory Analysts forthe Analysis of Nuclear Fuel Cycle Materials3. Summary of Test Method3.1 In controlled-potent
11、ial coulometry, the analyte reacts atan electrode 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 re
12、acted is calculable by Faradays law.Detailed discussions of the theory and applications of thistechnique are presented in Refs (1)4and (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
13、 saturatedcalomel electrode (SCE). Plutonium is then oxidized to Pu(IV)1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2005. Published December 2005. Origi
14、nallyapproved in 1990. Last previous edition approved in 2000 as C 1165 90 (2000)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary p
15、age onthe ASTM website.3Withdrawn.4The boldface numbers in parentheses refer to a list of references at the end ofthe text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.at a potential of + 0.670 V. The quantity of plutonium iscalcu
16、lated from the number of coulombs required for oxidationaccording to Faradays law.Q 5 *otidt5 nwF/M (1)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 = num
17、ber of coulombs to oxidize Pu(III) to Pu(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
18、0.5 M H2SO4electrolyte, the reductionpotential 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
19、few interferences at the selected potentialsof 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
20、of Pu(III) and Pu(IV).3.4 Sulfuric acid 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 electroly
21、tically inactive(3).4. Significance and 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 in
22、terferences are diverse metal ions thatoxidize 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 ox
23、idefuel, is iron (4). In the 0.5 M H2SO4electrolyte, 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). Al
24、ternatively, other techniques such as ICP, 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
25、since the uncertainty in the iron correctioncontributes 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 introd
26、uced as an impurity in reagents. Thesulfuric 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-hydrofluo
27、ric acid mixture or acid mixtures containingchloride 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 d
28、uring the electroly-sis.NOTE 1The purge 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
29、flow rateshould be such that no splashing occurs.6. Apparatus6.1 Controlled-Potential CoulometerA potentiostat hav-ing stable potential control at approximately 200 mAand 20 Vand an integrator capable of 0.05 % reproducibility are re-quired. The linearity of the integrator should be better than0.1 %
30、 for the selected range.NOTE 2To obtain maximum precision, it is recommended that thereference and sample aliquants contain approximately the same amount ofplutonium.56.2 Cell AssemblyA cell assembly similar to the onedescribed in Ref (5) has been used satisfactorily. Cell design is5The sole source
31、of supply of the apparatus known to the committee at this timeis EG begin stirring.10.5 Reduce Pu(IV) to Pu(III) at +0.310 V until the currentdecreases to 30 A.10.6 Reset the integrator and start timer.10.7 Oxidize Pu(III) to Pu(IV) at +0.670 V until the currentdecreases to 30 A. Record the coulomb
32、accumulation andelapsed time.NOTE 5All standards (reference material) and samples should befreshly fumed (within 4 h) prior to analysis.10.8 Remove the solution and thoroughly rinse the cell andelectrodes with 0.5 M H2SO4.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical
33、 Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockvil
34、le,MD.7Based upon Committee C26 Safeguards Matrix (C 1009, C 1068, C 1128,C 1156, C 1210, and C 1297).C 1165 90 (2005)310.9 Repeat 10.1-10.8 to attain a desired precision level forthe calibration.NOTE 6A recommended practice would be to intersperse standards(reference material) and samples during th
35、e time the analyses are beingdone.10.10 Calculate the calibration factor F byF 5 M/CC2 CB! (3)where:F = calibration factor, milligrams plutonium per cou-lomb,M = mass of plutonium in calibration reference aliquant,milligrams,CC= coulombs measured at 0.670 V electrolysis for cali-bration reference al
36、iquant, andCB= coulombs for blank measurement. Use the coulombvalue obtained on the blank for the elapsed time (tothe nearest minute) as that required for the referencealiquant oxidation time.11. Procedure11.1 Blanks:11.1.1 Obtain reproducible blank measurements on eachindividual platinum electrode
37、by following 11.1.2-11.1.8.NOTE 7Two platinum working electrodes are recommended to in-crease sample throughput by alternating the electrodes. While oneelectrode is being used in an electrolysis, the other electrode is beingcleaned by sitting in a beaker of hot concentrated nitric acid.The electrode
38、that is being cleaned is rinsed thoroughly with water and 0.5 M sulfuricacid prior to its use.11.1.2 Add 0.5 M H2SO4to the cell to completely immersethe working electrode.NOTE 8Avoid overfilling the cell. Fill only to the top of the platinumgauze working electrode. Overfilling the cell will result i
39、n longerelectrolysis times and larger background currents.11.1.3 Rinse the counter and reference electrode salt bridges(high-silica tubes) with 0.5 M H2SO4.11.1.4 Raise the cell into position firmly against the cellcover to ensure a tight fit. Purge the cell atmosphere withflowing argon or other ine
40、rt gas. (See Note 1.)11.1.5 Immediately connect the cell electrodes to the cou-lometer; begin stirring.11.1.6 Electrolyze the blank at 0.310Vuntil a 30-Acurrentis obtained.11.1.7 Start the timer, and electrolyze the blank at 0.670 Vfor a period of time that is consistent with sample electrolysistime
41、s.11.1.8 Record the number of coulombs at elapsed electroly-sis times consistent with sample electrolysis times.11.1.9 Following blanks, run a plutonium cell conditionersample to equilibrate the cell prior to running standards(reference material) and samples.NOTE 9A plutonium cell conditioner sample
42、 is a plutonium solutionthat is run through the complete reduction/oxidation cycle but is not usedfor calculation purposes. Experience has shown that if a plutonium cellconditioner is not run, the initial plutonium result will be low. A possiblecause for this effect is migration of plutonium into th
43、e high silica tubesuntil equilibration is attained.11.2 Sample Analysis:11.2.1 The plutonium-containing material may be dissolvedusing the appropriate dissolution procedure described in Prac-tice C 1168.11.2.2 After transferring and diluting, weigh aliquants con-taining 5 to 10 mg of plutonium.11.2.
44、3 Add 0.5 mLof 3 M H2SO4to each aliquant and fumeto dryness.11.2.4 After cooling, dissolve the sample using a minimalamount of 0.5 M H2SO4and again fume to dryness.11.2.5 Repeat 11.2.4.11.2.6 Dissolve the sample using a minimal amount of0.5 M H2SO4.11.2.7 Place a platinum working electrode in the ce
45、ll andcompletely immerse the working electrode using 0.5 M H2SO4.11.2.8 Proceed with the coulometric analysis of one or morealiquants by following 10.2-10.8.11.2.9 Correct for the iron content of the sample, which hasbeen determined using the recommended spectrophotometricprocedure or a suitable alt
46、ernate procedure.12. Calculation of Sample Result12.1 Calculate the plutonium content of the sample byPu 5 D! AS/AR! FCS2 CB!/MS(4)where:Pu = result, gram plutonium per gram sample,D = dilution factor, grams of diluted sample/gramsof aliquant analyzed,AS= atomic weight of plutonium in sample,AR= ato
47、mic weight of plutonium inplutonium metal reference material,F = average calibration factor, milligram plutoniumper coulomb (see 10.10),CS= coulombs measured for 0.670 V electrolysisfor sample aliquant,CB= coulombs for blank measurement(same elapsed time to the nearest minute as forsample), andMS= m
48、ass of solid sample initially dissolved,milligrams.12.2 Calculate the correction for iron byFec5 1026!Fe!AS/55.85! (5)where:Fec= correction for iron, gram plutonium/gramof sample,Fe = micrograms iron/gram of sample, andAS= atomic weight of plutonium in sample.12.3 Calculate the corrected plutonium c
49、ontent, Puc, of thesample byPuc5 Pu 2 Fec(6)13. Precision and Bias13.1 For a single measurement on an aliquant, the estimatedrepeatability relative standard deviation is 0.10 % and theestimated reproducibility relative standard deviation is 0.15 %.These estimates are based on the analysis of 5 samples, 4aliquants each, by each of 6 laboratories (6) and the analysis ofC 1165 90 (2005)4153 aliquants involving 9 distinct dissolutions of a controlsample at 1 laboratory. If more than one aliquant is measured(see 11.2.8) and the average reported, the repeatabili
