1、Designation:C126711Standard 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 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,commonly referred to as the ModifiedDavies and Gray technique,covers
3、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 types(1,2).2Details
4、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 stated in SI units are to
5、 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 det
6、ermine the applica-bility of regulatory limitations prior to use.For specificsafeguard and safety precaution statements,see Section 4.2.Referenced Documents2.1 ASTM Standards:3C696 Test Methods for Chemical,Mass Spectrometric,andSpectrochemical Analysis of Nuclear-Grade Uranium Di-oxide Powders and
7、PelletsC799 Test Methods for Chemical,Mass Spectrometric,Spectrochemical,Nuclear,and Radiochemical Analysis ofNuclear-Grade Uranyl Nitrate SolutionsC1128 Guide for Preparation of Working Reference Materi-als for Use in Analysis of Nuclear Fuel Cycle MaterialsC1204 Test Method for Uranium in Presence
8、 of Plutoniumby Iron(II)Reduction in Phosphoric Acid Followed byChromium(VI)TitrationC1346 Practice for Dissolution of UF6from P-10 Tubes,C1347 Practice for Preparation and Dissolution of UraniumMaterials for Analysis2.2 NIST Standard:4SRM 136e Potassium Dichromate(Oxidimetric Standard)2.3 NBL Stand
9、ard:5CRM 112A Uranium Metal Standard3.Summary of Test Method3.1 Samples are prepared by dissolution techniques detailedin Practices C1346,C1347,or Refs(2),(3),and(4).Appro-priate uncertainties for sampling and weight determinationshould be applied to the overall precision and bias calculationsfor th
10、e final result.Aliquants containing 20 to 200 mg ofuranium are prepared by weight.The sample is fumed todryness after the appropriate acid treatment.The sample isdissolved in dilute nitric acid or water prior to titration.3.2 Uranium is reduced to uranium(IV)by excess iron(II)inconcentrated phosphor
11、ic acid(H3PO4)containing sulfamicacid.The excess iron(II)is selectively oxidized by nitric acid(HNO3)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.3.3 The chromium(VI)titrant may be del
12、ivered manually ona weight or on a volumetric basis as specified by the facilitytitration procedure.3.3.1 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
13、.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 1,2011.Published June 2011.Originallyapproved in 1994.Last previous edition approved in 2006 as C1267 06.DOI:
14、10.1520/C1267-11.2The boldface 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 stan
15、dards Document Summary page 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:/www.nbl.doe.go
16、v.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.3.2 Automated titrators are facility specific and are notexplicitly addressed in this test method.However,automatedtitrators which have comparable bias and precision may beused.3.3.3 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 titrated is in
