1、Designation:C120414Standard Test Method forUranium in Presence of Plutonium by Iron(II)Reduction inPhosphoric Acid Followed by Chromium(VI)Titration1This standard is issued under the fixed designation C1204;the number immediately following the designation indicates the year oforiginal adoption or,in
2、 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 unirradiated uranium-plutoniummixed oxide having a uranium to plu
3、tonium ratio of 2.5 andgreater.The presence of larger amounts of plutonium(Pu)thatgive lower uranium to plutonium ratios may give low analysisresults for uranium(U)(1)2,if the amount of plutoniumtogether with the uranium is sufficient to slow the reductionstep and prevent complete reduction of the u
4、ranium in theallotted time.Use of this test method for lower uranium toplutonium ratios may be possible,especially when 20 to 50 mgquantities of uranium are being titrated rather than the 100 to300 mg in the study cited in Ref(1).Confirmation of thatinformation should be obtained before this test me
5、thod is usedfor ratios of uranium to plutonium less than 2.5.1.2 The amount of uranium determined in the data presentedin Section 12 was 20 to 50 mg.However,this test method,asstated,contains iron in excess of that needed to reduce thecombined quantities of uranium and plutonium in a solutioncontain
6、ing 300 mg of uranium with uranium to plutoniumratios greater than or equal to 2.5.Solutions containing up to300 mg uranium with uranium to plutonium ratios greater thanor equal to 2.5 have been analyzed(1)using the reagentvolumes and conditions as described in Section 10.1.3 The values stated in SI
7、 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 prac
8、tices and determine the applica-bility of regulatory limitations prior to use.For specific hazardstatements,see Section 8.2.Referenced Documents2.1 ASTM Standards:3C852 Guide for Design Criteria for Plutonium GloveboxesC1128 Guide for Preparation of Working Reference Materi-als for Use in Analysis o
9、f Nuclear Fuel Cycle MaterialsC1168 Practice for Preparation and Dissolution of PlutoniumMaterials for Analysis3.Summary of Test Method3.1 Samples are prepared by dissolution techniques detailedin Practice C1168 and Ref(2).Aliquants containing 20 to 300mg of uranium,as selected by the facility proce
10、dure,areprepared by weight.The sample is fumed to incipient drynessafter the addition of sulfuric acid.The sample is dissolved indilute sulfuric acid prior to titration.3.2 Uranium is reduced to uranium(IV)by excess ferrous(iron(II)in concentrated phosphoric acid(H3PO4)containingsulfamic acid.The ex
11、cess iron(II)is selectively oxidized bynitric acid(HNO3)in the presence of molybdenum(VI)cata-lyst.After the addition of vanadium(IV),the uranium(IV)istitrated with chromium(VI)to a potentiometric end point(3,4).3.3 A single chromium(VI)titrant delivered manually on aweight or volume basis is used.T
12、he concentration of thechromium(VI)solution is dependent upon the amount ofuranium being titrated(see 7.8).Automated titrators that havecomparable precisions can be used.NOTE1An alternative ceric(V)sulfate or nitrate titrant may also beused,providing that the user demonstrates equivalent performance
13、 to thedichromate titrant.3.4 For the titration of uranium alone,the precision of themodified Davies and Gray titration method has been signifi-cantly improved by increasing the amount of uranium titratedto 1 g and delivering about 90%of the titrant on a solid massbasis followed by titration to the
14、end point with a dilute titrant(5).This modification has not been studied for the titration ofuranium in the presence of plutonium,and confirmation of itsapplicability should be obtained by the facility prior to its use.1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel
15、Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1,2014.Published July 2014.Originally approvedin 1991.Last previous edition approved in 2008 as C1204 02(2008)1.DOI:10.1520/C1204-14.2The boldface numbers in parentheses refer to the list of
16、 references at the end ofthis test method.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 page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.5 The modification of the Davies and Gray titrationmethod,as described originally in Ref(4),may be used insteado
