ASTM C1267-17 Standard Test Method for Uranium by Iron (II) Reduction in Phosphoric Acid Followed by Chromium (VI) Titration in the Presence of Vanadium.pdf

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1、Designation: C1267 17Standard Test Method forUranium by Iron (II) Reduction in Phosphoric Acid Followedby Chromium (VI) Titration in the Presence of Vanadium1This standard is issued under the fixed designation C1267; the number immediately following the designation indicates the year oforiginal adop

2、tion 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, commonly referred to as the ModifiedDavies and Gray te

3、chnique, covers the titration of uranium inproduct, fuel, and scrap materials after the material is dis-solved. The test method is versatile and has been ruggednesstested. With appropriate sample preparation, this test methodcan give precise and unbiased uranium assays over a widevariety of material

4、 types (1, 2).2Details of the titrationprocedure in the presence of plutonium with appropriatemodifications are given in Test Method C1204.1.2 Uranium levels titrated are usually 20 to 50 mg, but upto 200 mg uranium can be titrated using the reagent volumesstated in this test method.1.3 The values s

5、tated 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,

6、 health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.For specific safeguard and safety precaution statements, seeSection 5.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-izati

7、on established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C696 Test Methods for Chemical, Mass Spectrometric, and

8、Spectrochemical Analysis of Nuclear-Grade Uranium Di-oxide Powders and PelletsC799 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and RadiochemicalAnalysis ofNuclear-Grade Uranyl Nitrate SolutionsC859 Terminology Relating to Nuclear MaterialsC1068 Guide for Qualification of

9、Measurement Methods bya Laboratory Within the Nuclear IndustryC1128 Guide for Preparation of Working Reference Materi-als for Use in Analysis of Nuclear Fuel Cycle MaterialsC1204 Test Method for Uranium in Presence of Plutoniumby Iron(II) Reduction in Phosphoric Acid Followed byChromium(VI) Titratio

10、nC1346 Practice for Dissolution of UF6from P-10 TubesC1347 Practice for Preparation and Dissolution of UraniumMaterials for Analysis2.2 NIST Standard:4SRM 136e Potassium Dichromate (Oxidimetric Standard)2.3 NBL Standard:5CRM 112A Uranium Metal Standard3. Terminology3.1 Except as otherwise defined he

11、rein, definitions of termsare as given in Terminology C859.4. Summary of Test Method4.1 Samples are prepared by dissolution techniques detailedin Practices C1346, C1347, or Refs (2), (3), and (4). Appro-priate uncertainties for sampling and weight determination1This test method is under the jurisdic

12、tion ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Nov. 1, 2017. Published November 2017. Originallyapproved in 1994. Last previous edition approved in 2011 as C1267 11. DOI:10.1520/C1267-17.2The boldface

13、numbers in parentheses refer to the list of references at the end ofthis standard.3For 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 pag

14、e onthe ASTM website.4Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.5New Brunswick Laboratory (NBL) Certified Reference Materials Catalog (U.S.Department of Energy), http:/science.energy.gov/nbl.Copyrig

15、ht ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of Internationa

16、l Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1should be applied to the overall precision and bias calculationsfor the final result. Aliquants containing 20 to 200 mg ofuranium are prepared by weight. The sample is fumed to

17、dryness after the appropriate acid treatment. The sample isdissolved in dilute nitric acid or water prior to titration.4.2 Uranium is reduced to uranium(IV) by excess iron(II) inconcentrated phosphoric acid (H3PO4) containing sulfamicacid. The excess iron(II) is selectively oxidized by nitric acid(H

18、NO3) in the presence of a molybdenum(VI) catalyst. Afterthe addition of a vanadium(IV) solution, the uranium(IV) istitrated with chromium(VI) to a potentiometric end point.4.3 The chromium(VI) titrant may be delivered manually ona weight or on a volumetric basis as specified by the facilitytitration

19、 procedure.4.3.1 If the titrant is delivered on a volumetric basis,corrections to the volume of titrant may be needed to adjust forthe difference between the temperature of preparation and theambient temperature.4.3.2 Automated titrators are facility specific and are notexplicitly addressed in this

20、test method. However, automatedtitrators which have comparable bias and precision may beused.4.3.3 There is an alternate, high precision (;0.005 % RSD)modified Davies and Gray titration, which is similar to themethod covered in this procedure. In the high precisionmethod, the amount of uranium titra

21、ted is increased and about90 % of the titrant is delivered on a solid weight basis followedby titration to the end point with a dilute titrant. Details of thisalternate method are available in Ref (5).5. Significance and Use5.1 Factors governing selection of a method for the deter-mination of uraniu

22、m include available quantity of sample,homogeneity of material sampled, sample purity, desired levelof reliability, and facility available equipment.5.2 This uranium assay method is referenced in the TestMethods for Chemical, Mass Spectrometric, and Spectro-chemical Analysis of Nuclear-Grade Uranium

23、 Dioxide Pow-ders and Pellets (Test Methods C696) and in the Test Methodsfor Chemical, Mass Spectrometric, and Spectrochemical,Nuclear, and RadiochemicalAnalysis of Nuclear-Grade UranylNitrate Solutions (Test Methods C799). This uranium assaymethod may also be used for uranium hexafluoride anduraniu

24、m ore concentrate. This test method determines 20 to200 mg of uranium; is applicable to product, fuel, and scrapmaterial after the material is dissolved; is tolerant towards mostmetallic impurity elements usually specified in product andfuel; and uses no special equipment.5.3 The ruggedness of the t

25、itration method has been studiedfor both the volumetric (6) and the weight (7) titration ofuranium with dichromate.5.4 Fitness for Purpose of Safeguards and Nuclear SafetyApplicationMethods intended for use in safeguards andnuclear safety applications shall meet the requirements speci-fied by Guide

26、C1068 for use in such applications.5.4.1 When used in conjunction with the appropriate certi-fied reference materials (SRM6or CRM), this procedure candemonstrate traceability to the national measurement base.However, use of the test method does not automaticallyguarantee regulatory acceptance of the

27、 resulting safeguardsmeasurements. It remains the sole responsibility of the user ofthis test method to assure that its application to safeguards hasthe approval of the proper regulatory authorities.6. Interferences6.1 Interfering elements are not generally present in productand fuel material in qua

28、ntities which cause interference in thetitration.6.1.1 Of the metallic impurity elements usually included inspecifications for product and fuel, silver, manganese, andvanadium (in the V oxidation state) interfere when present inamounts of 10 mg or greater of impurity per 100 mg ofuranium (2, 8).6.1.

29、2 Silver and vanadium (in the V oxidation state) causepositive bias when present in milligram quantities in thesample. The aliquant treatment adjusts the oxidation state ofany vanadium(V) present in the sample (2). To remove silver,the sample must be treated prior to titration (8).6.1.3 Manganese wa

30、s originally found to cause a negativebias (2), but this bias is eliminated when the titration aliquantpreparation procedure is followed as given (9, 10) in thistitrimetric method.6.2 Interferences with the Modified Davies and Graytitration, which may be present in some uranium materials,have been s

31、ystematically studied.6.2.1 The non-interference of copper, titanium, cobalt,nickel, cerium, and samarium was demonstrated (11) at the 50mg impurity level for 100 mg of uranium.6.2.2 The effects of the following elements in milligramquantities were studied: silver, gold, lead, iodine, arsenic,antimo

32、ny, and bismuth (8).6.2.2.1 Gold, lead, arsenic(V), antimony(V), and bismuthdo not interfere when present in amounts of 10 mg for 100 mgof uranium.6.2.2.2 Silver, iodine, arsenic(III), and antimony(III) inter-fere seriously in the determination of uranium and must beeliminated prior to titration.6.2

33、.3 The effects of impurities on the titration of uraniumcontinued with the platinum metals (ruthenium, rhodium,palladium, osmium, iridium, and platinum), chloride, bromide(12), fluoride (13), and technetium (14).6.2.3.1 Ruthenium, palladium, osmium, iridium, and plati-num cause serious positive erro

34、rs in the determination ofuranium. Rhodium alone among the platinum metals does notcause any significant error.6.2.3.2 Chloride and bromide interfere with the assaythrough their effect on the platinum indicator electrode.6.2.3.3 Small amounts of fluoride, less than 400 mg ashydrofluoric acid (HF) or

35、 600 mg if HNO3is present, can betolerated by the titration.6SRM is a registered trademark.C1267 1726.2.3.4 Technicium, found in high temperature reactor graderecycle (htgr) fuel, interferes with the titration and must beremoved before titration.6.3 The removal of certain interferences in the modifi

36、edDavies and Gray titration has also been studied.6.3.1 The initial fuming of titration aliquants with sulfuricacid removes impurity elements such as the halides and volatilemetallic elements (2, 12, 13).6.3.2 Arsenic(III) and antimony(III) can be eliminated inthe H3PO4by potassium dichromate (K2Cr2

37、O7) oxidation priorto its addition to the titration medium (8).6.3.3 Elimination of interferences in the titration bymercury, platinum, and palladium by means of a coppercolumn was evaluated (15).6.3.4 Elimination of interferences by solvent extraction ofthe uranium from the impurities has also been

38、 studied (16).6.4 A list of impurities with brief references to their treat-ment for elimination is given in Table A1.1 in Annex A1, andthe details are given in Refs 2, 8, 9, 10, and 12-16.7. Apparatus7.1 Buret, polyethylene bottle (preparation instructions canbe found in Appendix X1), glass weight,

39、 or glass volumetric.7.2 pH Meter, with indicator (a 16-gauge platinum wire hasbeen found to be satisfactory) and reference (saturated calomelhas been found to be satisfactory) electrodes.7.2.1 The indicator electrode should be changed or cleanedif there is a titration problem such as less distinct

40、than normalend point break or end point drift, or, if desired, prior to usewhen more than a week has passed since its last use. Suggestedcleaning procedures for platinum wire electrodes are detailedin Appendix X2.7.2.2 Asbestos and glass bead tipped saturated calomelelectrodes can be placed directly

41、 in the titration solution. Glassfrit tipped saturated calomel electrodes may have a faster leakrate and may need to be used with a separator tube containingthe electrolyte to prevent titration problems due to chloride.7.2.3 The reference electrode should be covered with arubber tip or submerged in

42、a solution (saturated potassiumchloride solution for the calomel electrode) for overnightstorage.7.3 Magnetic Stirrer and TFE-Fluorocarbon Coated Mag-net.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents co

43、nform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.7Other grades of reagentsmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accu

44、racy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean laboratory accepteddemineralized or deionized water.8.3 Ferrous Sulfate Heptahydrate (FeSO47 H2O, 1.0 M)Add 100 mL of sulfuric acid (H2SO4, sp gr 1.84) to 750 mL ofwater as the sol

45、ution is stirred.Add 280 g of FeSO47 H2O, anddilute the solution to 1 L with water. Prepare the FeSO47 H2Oreagent fresh, weekly. See the Note 5 in 11.8 on combination ofthis reagent with the H3PO4.8.4 Nitric Acid (HNO3, 8 M)Add 500 mL of HNO3(sp gr1.42) to 10 % Au Reduce the gold to metal and separa

46、te (8).Am, Sb, As, Br, Cl, Fe, Au, Pb, Ir, Mn, Hg, Mo,Np, Os, Pd, Pt, Pu, Ru, Ag, Th, Sn, V, ZrUse the tributyl phosphate/carbon tetrachloride extraction technique (16). Alternate solvents such as dodecaneare now used.AThe potassium dichromate oxidizes these elements to a non-interfering oxidation s

47、tate which the ferrous ion is not capable of reducing.C1267 178X2. PLATINUM WIRE ELECTRODE TREATMENTSX2.1 A routine platinum wire electrode cleaning treatmentand the treatment for restoring fast response to a sluggishplatinum electrode is flaming to white heat with immediateimmersion in concentrated

48、 nitric acid; the process is usuallydone at least two times.X2.2 An alternate cleaning method for the platinum wireelectrodes is to soak the electrode in hydrofluoric acid prior toflaming and nitric acid immersion as detailed in X2.1.X2.3 If the analyses of standards show increasing bias overthe day

49、s analyses after routine cleaning, for several consecu-tive days, a sodium bisulfate fusion of the platinum wireelectrode may be needed.After the sodium bisulfate fusion andflaming, again perform the routine cleaning in X2.1.X3. DICHROMATE SOLUTION STANDARDIZATIONX3.1 Standardize reagent grade or better potassium dichro-mate against CRM 112-A uranium metal or its equivalent (seeAppendix X4).X3.2 The standard deviation of the mean for the potassiumdichromate standardization s/=n! should be well within theaccepted laboratory error limits for the uranium titration whenn =