ASTM_C_1165_-_12.pdf

Designation:C116512Standard 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 case 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 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 recommended 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 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 regulatory limitations 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 ofNuclear-Grade Plutonium MetalC759 Test Methods for Chemical,Mass Spectrometric,Spectrochemical,Nuclear,and Radiochemical Analysis ofNuclear-Grade Plutonium Nitrate SolutionsC833 Specification for Sintered(Uranium-Plutonium)Diox-ide PelletsC859 Terminology Relating to Nuclear MaterialsC1009 Guide for Establishing and Maintaining a QualityAssurance Program forAnalytical Laboratories Within theNuclear IndustryC1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1108 Test Method for Plutonium by Controlled-PotentialCoulometryC1128 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 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 Analysis of Nuclear Fuel Cycle Materials3.Summary of Test Method3.1 In controlled-potential 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 reacted is calculable by Faradays law.Detailed 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 is then oxidized to Pu(IV)at a potential of+0.670 V.The quantity of plutonium is1This 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 1,2012.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 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 calculated from the number of coulombs required for oxidationaccording to Faradays law.Q 5*oti dt5 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 isoto-pic composition),grams/equivalent,Q=number 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 0.5 M H2SO4electrolyte