1、Designation: C1165 12C1165 17Standard Test Method forDetermining Plutonium by Controlled-Potential Coulometryin H2SO4 at a Platinum Working Electrode1This standard is issued under the fixed designation C1165; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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 milligram quantities of plutonium i
3、n unirradiated uranium-plutonium mixedoxide having a U/Pu ratio range of 0.1 to 10. This test method is also applicable to plutonium metal, plutonium oxide,uranium-plutonium mixed carbide, various plutonium compounds including fluoride and chloride salts, and plutonium solutions.1.2 The recommended
4、amount of plutonium for each aliquant in the coulometric analysis is 5 to 10 mg. Precision worsens forlower amounts of plutonium, and elapsed time of electrolysis becomes impractical for higher amounts of plutonium.1.3 The values stated in SI units are to be regarded as standard. No other units of m
5、easurement are included in this standard.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 safety safety, health, and healthenvironmental practices and determine the
6、applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 89.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of In
7、ternational Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C757 Specification for Nuclear-Grade Plutonium Dioxide Powder for Light Water ReactorsC758 Test Methods for Chemical, Mass Sp
8、ectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Plutonium MetalC759 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Plutonium Nitrate SolutionsC833 Specification for Sintered (Uranium-Plutonium) D
9、ioxide Pellets for Light Water ReactorsC859 Terminology Relating to Nuclear MaterialsC1009 Guide for Establishing and Maintaining a Quality Assurance Program for Analytical Laboratories Within the NuclearIndustryC1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear
10、IndustryC1108 Test Method for Plutonium by Controlled-Potential CoulometryC1128 Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Calibration for a Measurement Method Used to Analyze Nuclear Fuel Cycle MaterialsC1168
11、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 IndustryC1297 Guide for Qualification of Laboratory Analysts for the Analysis of Nuclear Fuel
12、Cycle Materials3. Terminology3.1 Except as otherwise defined herein, definitions of terms are as given in Terminology C859.1 This test method is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.Current editi
13、on approved June 1, 2012Nov. 1, 2017. Published June 2012November 2017. Originally approved in 1990. Last previous edition approved in 20052012 asC1165 90 (2005).C1165 12. DOI: 10.1520/C1165-12.10.1520/C1165-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Custo
14、mer 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 standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the
15、 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 cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright AS
16、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 In controlled-potential coulometry, the analyte reacts at an electrode having a maintained potential that precludes reactionsof as many impurity components as is feasibl
17、e. In the electrolysis, current decreases exponentially as the reaction proceeds untila selected background current is reached. The quantity of analyte reacted is calculable by Faradays law. Detailed discussions ofthe theory and applications of this technique are presented in Refs (1)3 and (2).4.2 P
18、lutonium and many impurity element ions are initially reduced in a 0.5 M H2SO4 electrolyte at a platinum workingelectrode (3) maintained at + 0.310 V versus a saturated calomel electrode (SCE). Plutonium is then oxidized to Pu(IV) at apotential of + 0.670 V. The quantity of plutonium is calculated f
19、rom the number of coulombs required for oxidation according toFaradays law.Q 5*ot i dt5nwF/M (1)Rearrangement to solve for w gives:w 5MQ/nF (2)where:w = weight of Pu(III) oxidized to Pu(IV), g,M = gram-molecular mass of plutonium (adjusted for isotopic composition), grams/equivalent,Q = number of co
20、ulombs to oxidize Pu(III) to Pu(IV), coulombs,n = number of electron change to oxidize Pu(III) to Pu(IV) = 1, andF = Faraday constant, coulomb/equivalent.4.3 An electrolyte of sulfuric acid, that selectively complexes Pu(IV), provides very reproducible electrolysis of Pu(III) toPu(IV). In a 0.5 M H2
21、SO4 electrolyte, the reduction potential of + 0.310 V for conversion of Pu(IV and VI) to Pu(III) and theoxidation potential of + 0.670 V for conversion of Pu(III) to Pu(IV) accounts for about 99.9 % (as calculated from the Nernstequation) conversion of the total plutonium in solution. There are few
22、interferences at the selected potentials of the metallicimpurities usually listed in specifications for fast breeder reactor (FBR) mixed oxide fuel.Achemical calibration of the coulometricsystem using the selected potentials technique is necessary to correct for the less than 100 % conversions of Pu
23、(III) and Pu(IV).4.4 Sulfuric acid is a convenient electrolyte since it is used for preliminary fuming of samples to volatilize interferingcomponents (see 5.36.3 and 5.46.4). The preliminary fuming with sulfuric acid also serves to depolymerize any polymericplutonium species, which tend to be electr
24、olytically inactive (3).5. Significance and Use5.1 This test method is to be used to ascertain whether or not materials meet specifications for plutonium content or plutoniumassay, or both.5.2 A chemical calibration of the coulometer is necessary for accurate results.5.3 Fitness for Purpose of Safeg
25、uards and Nuclear Safety ApplicationMethods intended for use in safeguards and nuclearsafety applications shall meet the requirements specified by Guide C1068 for use in such applications.3 The boldface numbers in parentheses refer to a list of references at the end of the text.FIG. 1 Example of a C
26、ell Design Used at Los Alamos National Laboratory (LANL)C1165 1726. Interferences6.1 Categories of interferences are diverse metal ions that oxidize or reduce at the potential of + 0.670 V used for the oxidationof Pu(III) to Pu(IV), organic matter, anions that complex plutonium, and oxygen.6.2 The m
27、ajor interfering metallic impurity element, of those usually included in specifications for FBR mixed oxide fuel, isiron (4). In the 0.5 M H2SO4 electrolyte, the Fe(II) Fe(III) and Pu(III) Pu(IV) couples have essentially the same Eo valueof + 0.490 V. The iron interference, therefore, is quantitativ
28、e and is corrected based on its measured value that can be determinedby a spectrophotometric method (5). Alternatively, other techniques such as ICP, DCP, or emission spectrometry can also be usedif the iron content is sufficiently low. When the iron result is 20 g/g, the lower limit of the spectrop
29、hotometric method, nocorrection is necessary. The best available method for iron determination is recommended since the uncertainty in the ironcorrection contributes to the uncertainty in the plutonium value.6.3 Organic matter usually is not present in calcined mixed oxide fuel pellets nor in mixed
30、oxide powder blends prepared usingcalcined uranium oxide and calcined plutonium oxide. However, it may be introduced as an impurity in reagents. The sulfuric acidfuming of reference material and of samples that precedes the coulometric analysis volatilizes most organic components.6.4 The sulfuric ac
31、id fuming volatilizes nitrate, nitrite, fluoride, and chloride, that are introduced by the use of anitric-hydrofluoric acid mixture or acid mixtures containing chloride for the dissolution of samples and interfere in the coulometricdetermination of plutonium.6.5 Oxygen interferes and must be purged
32、continuously from both the solution and atmosphere in the electrolysis cell with anoxygen-free inert gas before and during the electrolysis.NOTE 1The purge gas tube extends through the cell cover and is positioned approximately 1 cm above the sample solution in the cell. The inert gasflow is maintai
33、ned at a flow rate that causes a dimple to be seen on the surface of the solution with the stirrer off. The inert gas flow rate should be suchthat no splashing occurs.6.6 Nitric acid and hydrofluoric acid must be added during the preparation of the plutonium metal to ensure oxidation of theplutonium
34、 to Pu(IV) and to match the acid matrix from plutonium oxide dissolution. Plutonium that is dissolved in onlyhydrochloric acid and then evaporated to dryness in sulfuric acid while in the Pu(III) oxidation state will contain tiny blue crystalswithin the pink plutonium (IV) sulfate material, and lowe
35、r recoveries are experienced during the coulometric measurement. Bluecrystals are not observed when plutonium oxide materials are dissolved in HNO3 and HF acids and subsequently fumed to drynessin H2SO4.6.7 Due to a slight overlap between the potential at which Np(VI) reduces to Np(V), +0.660 V, and
36、 the potential used in thecurrent method to oxidize Pu(III) to Pu(IV), +0.670 V, a large amount of neptunium will cause the plutonium assay to be biasedhigh and not accurately reflect the plutonium content of the material being analyzed. Thus, neptunium can only be tolerated up to1 % in the sample,
37、above that level the neptunium must be removed prior to the sample undergoing the coulometry process.7. Apparatus7.1 Controlled-Potential CoulometerApotentiostat having stable potential control at approximately 200 mAand 20 V and anintegrator capable of 0.05 % reproducibility are required. The linea
38、rity of the integrator should be better than 0.1 % for the selectedrange.47.2 Cell AssemblyA cell assembly similar to the one described in Ref (5) has been used satisfactorily. Cell design is verycritical in controlled-potential coulometry. There are many factors that must be considered in choosing
39、or designing a cellassembly. It is beyond the scope of this test method to describe all of the factors that should be considered. A thorough detaileddiscussion of electrolysis cell design is presented in Ref (2).NOTE 2Drawing (see Fig. 1) of a cell design that has been successfully used at the Los A
40、lamos National Laboratory. The titration cell consists ofa 50 mL cut off beaker.7.3 Timer or stopwatch for measuring electrolysis times (capable of measuring in seconds).8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended th
41、at allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where suchspecifications are available.5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening
42、 the accuracy of the determination.4 Coulometer suppliers or designers who have reported instrument performances that are consistent with the specification provided in this standard include: the SRNLCoulometer, Savannah River National Laboratory, Aiken, South Carolina, USA; the Mayak Coulometer PIK-
43、200, Ozersk, Russia; and the coulometer at the LAMMLaboratory, CEA Centre de Marcoule, Bagnols-sur-CreCedex, France. If you are aware of alternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of the resp
44、onsible technical committee,1 which you may attend.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd.,
45、 Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.C1165 1738.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean distilled or deionized water.8.3 Argon, Oxygen-Free (99.99
46、 %)Helium, nitrogen, or other pure inert gas may be used.8.4 Hydrochloric Acid (HCl, 10.9 M)Concentrated HCl, ACS ultratrace grade.8.5 Hydrochloric Acid (HCl, 6 M)Add 500 mL of concentrated 10.9 M HCl to less than 500 mL of water and dilute to 1 Lwith water.8.6 Hydrochloric Acid (HCl, 1.0 M)Add 82.6
47、 mL of concentrated 10.9 M HCl to water and dilute to 1L.1 L.8.7 Hydrofluoric Acid (HF, 29M)Concentrated HF, ACS ultratrace grade.8.8 Hydrofluoric Acid (HF, 1.3 M)Add 4.8 mL of concentrated 29 M HF to water and dilute to 100 mL.8.9 Nitric Acid (HNO3, 15.9 M)Concentrated HNO3, ACS ultratrace grade.8.
48、10 Sulfuric Acid (H2SO4, 18.1 M)Concentrated H2SO4 , ACS ultratrace grade.8.11 Sulfuric Acid (3 M)Add 168 mL of concentrated H2SO4 to water, while stirring, and dilute to 1 L with water.8.12 Sulfuric Acid (0.5 M)Add 28 mL of concentrated H2SO4 to water, while stirring, and dilute to 1 L with water.8
49、.13 Plutonium Reference SolutionDissolve a weighed quantity (balance capable of weighing to 0.01 mg) of 0.5 to 1 g of NBL(Note 4) CRM 126 metal (or its replacement) cleaned per certificate directions in 6 M HCl. Use a sufficient amount of 6 M HClto maintain an acid concentration of 1 to 2 M. Completely transfer the solution with 1.0 M HCl rinses to a tared container, diluteto 100 to 200 g with 1.0 M HCl(to HCl (to give a plutonium concentration of 5 mg/g), and weigh.NOTE 3A tared polyethylene bottle has been used successfully to dispense weighed aliq
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