1、Designation: C1267 11C1267 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 oforigi
2、nal 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, commonly referred to as the Modified Davies an
3、d Gray technique, covers the titration of uranium inproduct, fuel, and scrap materials after the material is dissolved. The test method is versatile and has been ruggedness tested. Withappropriate sample preparation, this test method can give precise and unbiased uranium assays over a wide variety o
4、f material types(1, 2).2 Details of the titration procedure in the presence of plutonium with appropriate modifications are given in Test MethodC1204.1.2 Uranium levels titrated are usually 20 to 50 mg, but up to 200 mg uranium can be titrated using the reagent volumes statedin this test method.1.3
5、The values stated in SI units are to be regarded as standard. No other units of measurement 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 appro
6、priate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. For specific safeguard and safety precaution statements, see Section 45.1.5 This international standard was developed in accordance with internationally recognized p
7、rinciples on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C696 Test Methods for Chemical
8、, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium DioxidePowders and PelletsC799 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Uranyl Nitrate SolutionsC859 Terminology Relating to Nuclear MaterialsC1068
9、Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear IndustryC1128 Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle MaterialsC1204 Test Method for Uranium in Presence of Plutonium by Iron(II) Reduction in Phosphoric Acid Foll
10、owed byChromium(VI) TitrationC1346 Practice for Dissolution of UF6 from P-10 TubesC1347 Practice for Preparation and Dissolution of Uranium Materials for Analysis2.2 NIST Standard:4SRM 136e Potassium Dichromate (Oxidimetric Standard)2.3 NBL Standard:5CRM 112A Uranium Metal Standard1 This test method
11、 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 edition approved June 1, 2011Nov. 1, 2017. Published June 2011November 2017. Originally approved in 1994. Last previous edition approved in 200620
12、11 asC1267 06.C1267 11. DOI: 10.1520/C1267-11.10.1520/C1267-17.2 The boldface numbers in parentheses refer to the list of references at the end of this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of
13、 ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.5 New Brunswick Laboratory (NBL) Certified Reference
14、Materials Catalog (U.S. Department of Energy), http:/www.nbl.doe.gov.http:/science.energy.gov/nbl.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 previous version. Becauseit may not be technically
15、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 ASTM International, 100 Barr Harbor Drive, PO Box C700
16、, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Except as otherwise defined herein, definitions of terms are as given in Terminology C859.4. Summary of Test Method4.1 Samples are prepared by dissolution techniques detailed in Practices C1346, C1347, or Refs (2), (3), and (4). App
17、ropriateuncertainties for sampling and weight determination should be applied to the overall precision and bias calculations for the finalresult.Aliquants containing 20 to 200 mg of uranium are prepared by weight. The sample is fumed to dryness after the appropriateacid treatment. The sample is diss
18、olved in dilute nitric acid or water prior to titration.4.2 Uranium is reduced to uranium(IV) by excess iron(II) in concentrated phosphoric acid (H3PO4) containing sulfamic acid.The excess iron(II) is selectively oxidized by nitric acid (HNO3) in the presence of a molybdenum(VI) catalyst. After the
19、additionof a vanadium(IV) solution, the uranium(IV) is titrated with chromium(VI) to a potentiometric end point.4.3 The chromium(VI) titrant may be delivered manually on a weight or on a volumetric basis as specified by the facilitytitration procedure.4.3.1 If the titrant is delivered on a volumetri
20、c basis, corrections to the volume of titrant may be needed to adjust for thedifference between the temperature of preparation and the ambient temperature.4.3.2 Automated titrators are facility specific and are not explicitly addressed in this test method. However, automated titratorswhich have comp
21、arable bias and precision may be used.4.3.3 There is an alternate, high precision (;0.005 % RSD) modified Davies and Gray titration, which is similar to the methodcovered in this procedure. In the high precision method, the amount of uranium titrated is increased and about 90 % of the titrantis deli
22、vered on a solid weight basis followed by titration to the end point with a dilute titrant. Details of this alternate method areavailable in Ref (5).5. Significance and Use5.1 Factors governing selection of a method for the determination of uranium include available quantity of sample, homogeneityof
23、 material sampled, sample purity, desired level of reliability, and facility available equipment.5.2 This uranium assay method is referenced in the Test Methods for Chemical, Mass Spectrometric, and SpectrochemicalAnalysis of Nuclear-Grade Uranium Dioxide Powders and Pellets (Test Methods C696) and
24、in the Test Methods for Chemical,Mass Spectrometric, and Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Uranyl Nitrate Solutions (TestMethods C799). This uranium assay method may also be used for uranium hexafluoride and uranium ore concentrate. This testmethod determines 20 t
25、o 200 mg of uranium; is applicable to product, fuel, and scrap material after the material is dissolved; istolerant towards most metallic impurity elements usually specified in product and fuel; and uses no special equipment.5.3 The ruggedness of the titration method has been studied for both the vo
26、lumetric (6) and the weight (7) titration of uraniumwith dichromate.5.4 Committee C26 Safeguards Statement: Fitness for Purpose of Safeguards and Nuclear Safety Application4.4.1 The materials (nuclear grade uranium in product, fuel, and scrap) to which this test method applies are subject to nuclear
27、safeguard regulations governing their possession and use. The analytical method in this standard meets U.S. Department of Energyguidelines for acceptability of a measurement method for generation of safeguards accountability measurement data.Methodsintended for use in safeguards and nuclear safety a
28、pplications shall meet the requirements specified by Guide C1068 for use in suchapplications.5.4.1 When used in conjunction with the appropriate certified reference materials (SRM6 or CRM), this procedure candemonstrate traceability to the national measurement base. However, use of the test method d
29、oes not automatically guaranteeregulatory acceptance of the resulting safeguards measurements. It remains the sole responsibility of the user of this test methodto assure that its application to safeguards has the approval of the proper regulatory authorities.6. Interferences6.1 Interfering elements
30、 are not generally present in product and fuel material in quantities which cause interference in thetitration.6.1.1 Of the metallic impurity elements usually included in specifications for product and fuel, silver, manganese, and vanadium(in the V oxidation state) interfere when present in amounts
31、of 10 mg or greater of impurity per 100 mg of uranium (2, 8).6.1.2 Silver and vanadium (in the V oxidation state) cause positive bias when present in milligram quantities in the sample. Thealiquant treatment adjusts the oxidation state of any vanadium(V) present in the sample (2). To remove silver,
32、the sample must betreated prior to titration (8).6.1.3 Manganese was originally found to cause a negative bias (2), but this bias is eliminated when the titration aliquantpreparation procedure is followed as given (9, 10) in this titrimetric method.6 SRM is a registered trademark.C1267 1726.2 Interf
33、erences with the Modified Davies and Gray titration, which may be present in some uranium materials, have beensystematically studied.6.2.1 The non-interference of copper, titanium, cobalt, nickel, cerium, and samarium was demonstrated (11) at the 50 mgimpurity level for 100 mg of uranium.6.2.2 The e
34、ffects of the following elements in milligram quantities were studied: silver, gold, lead, iodine, arsenic, antimony,and bismuth (8).6.2.2.1 Gold, lead, arsenic(V), antimony(V), and bismuth do not interfere when present in amounts of 10 mg for 100 mg ofuranium.6.2.2.2 Silver, iodine, arsenic(III), a
35、nd antimony(III) interfere seriously in the determination of uranium and must be eliminatedprior to titration.6.2.3 The effects of impurities on the titration of uranium continued with the platinum metals (ruthenium, rhodium, palladium,osmium, iridium, and platinum), chloride, bromide (12), fluoride
36、 (13), and technetium (14).6.2.3.1 Ruthenium, palladium, osmium, iridium, and platinum cause serious positive errors in the determination of uranium.Rhodium alone among the platinum metals does not cause any significant error.6.2.3.2 Chloride and bromide interfere with the assay through their effect
37、 on the platinum indicator electrode.6.2.3.3 Small amounts of fluoride, less than 400 mg as hydrofluoric acid (HF) or 600 mg if HNO3 is present, can be toleratedby the titration.6.2.3.4 Technicium, found in high temperature reactor grade recycle (htgr) fuel, interferes with the titration and must be
38、removed before titration.6.3 The removal of certain interferences in the modified Davies and Gray titration has also been studied.6.3.1 The initial fuming of titration aliquants with sulfuric acid removes impurity elements such as the halides and volatilemetallic elements (2, 12, 13).6.3.2 Arsenic(I
39、II) and antimony(III) can be eliminated in the H3PO4 by potassium dichromate (K2Cr2O7) oxidation prior to itsaddition to the titration medium (8).6.3.3 Elimination of interferences in the titration by mercury, platinum, and palladium by means of a copper column wasevaluated (15).6.3.4 Elimination of
40、 interferences by solvent extraction of the uranium from the impurities has also been studied (16).6.4 Alist of impurities with brief references to their treatment for elimination is given inTable A1.1 in AnnexA1, and the detailsare given in Refs 2, 8, 9, 10, and 12-16.7. Apparatus7.1 Buret, polyeth
41、ylene bottle (preparation instructions can be found in Appendix X1), glass weight, or glass volumetric.7.2 pH Meter, with indicator (a 16-gauge platinum wire has been found to be satisfactory) and reference (saturated calomel hasbeen found to be satisfactory) electrodes.7.2.1 The indicator electrode
42、 should be changed or cleaned if there is a titration problem such as less distinct than normal endpoint break or end point drift, or, if desired, prior to use when more than a week has passed since its last use. Suggested cleaningprocedures for platinum wire electrodes are detailed in Appendix X2.7
43、.2.2 Asbestos and glass bead tipped saturated calomel electrodes can be placed directly in the titration solution. Glass frittipped saturated calomel electrodes may have a faster leak rate and may need to be used with a separator tube containing theelectrolyte to prevent titration problems due to ch
44、loride.7.2.3 The reference electrode should be covered with a rubber tip or submerged in a solution (saturated potassium chloridesolution for the calomel electrode) for overnight storage.7.3 Magnetic Stirrer and TFE-Fluorocarbon Coated Magnet.8. Reagents8.1 Purity of ReagentsReagent grade chemicals
45、shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where suchspecifications are available.7 Other grades of reagents may be used, provided it is first ascertain
46、ed that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean laboratory accepteddemineralized or deionized water.7 Reagent Chemicals, American Che
47、mical 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., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S.
48、 Pharmacopeial Convention, Inc. (USPC), Rockville, MD.C1267 1738.3 Ferrous Sulfate Heptahydrate (FeSO47 H2O, 1.0 M)Add 100 mLof sulfuric acid (H2SO4, sp gr 1.84) to 750 mLof wateras the solution is stirred. Add 280 g of FeSO47 H2O, and dilute the solution to 1 L with water. Prepare the FeSO47 H2O re
49、agentfresh, weekly. See the Note 5 in 10.811.8 on combination of this reagent with the H3PO4.8.4 Nitric Acid (HNO3, 8 M)Add 500 mL of HNO3 (sp gr 1.42) to 10 % Au Reduce the gold to metal and separate (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.A The potassium dichromate oxidizes these elements to a non-interfering oxidation state which the ferrous ion is not capable of reducing.C1267 179A2.1 Add
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