1、Designation: C 1204 02Standard Test Method forUranium in the Presence of Plutonium by Iron(II) Reductionin Phosphoric Acid Followed by Chromium(VI) Titration1This standard is issued under the fixed designation C 1204; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers unirradiated uranium-plutoniummixed oxide havi
3、ng a uranium to plutonium 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 co
4、mplete reduction of the uranium 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
5、 obtained before this test method 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 a
6、nd plutonium in a solutioncontaining 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 Se
7、ction 10.1.3 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 determine the applica-bility of regulatory limitations prior to use. For s
8、pecific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:C 852 Guide for Design Criteria for Plutonium Gloveboxes3C 1128 Guide for Preparation of Working Reference Mate-rials for Use in the Analysis of Nuclear Fuel CycleMaterials3C 1168 Practice for Preparation and Dissoluti
9、on of Pluto-nium Materials for Analysis33. Summary of Test Method3.1 Samples are prepared by dissolution techniques detailedin Practice C 1168 and Ref (2). Aliquants containing 20 to 300mg of uranium, as selected by the facility procedure, areprepared by weight. The sample is fumed to incipient dryn
10、essafter 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 excess iron(II) is selectively oxidized bynitric acid (HNO3)
11、 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. The concentration of thechromium(VI) solution i
12、s dependent upon the amount ofuranium being titrated (see 7.8). Automated titrators that havecomparable precisions can be used.NOTE 1An alternative ceric (V) sulfate or nitrate titrant may also beused, providing that the user demonstrates equivalent performance to thedichromate titrant.3.4 For the t
13、itration of uranium alone, the precision of themodified Davies and Gray titration method has been improvedby increasing the amount of uranium titrated to1ganddelivering about 90 % of the titrant on a solid mass basisfollowed by titration to the end point with a dilute titrant (5).This modification h
14、as 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.3.5 The modification of the Davies and Gray titrationmethod, as described originally in Ref (4), may be used insteadof the method des
15、cribed herein, where laboratories havedemonstrated no plutonium interference at the uranium toplutonium ratios and amounts titrated at that facility. If anymodification is made to the procedure in Ref (4) for applicationat the facility to uranium, plutonium mixed oxides, confirma-tion that the modif
16、ication does not degrade the analysis1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Jan. 10, 2002. Published April 2002. Originallypublished as C 120491. Last pr
17、evious edition C 120491(1996).2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.3Annual Book of ASTM Standards, Vol 12.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.technique as s
18、tated should be demonstrated prior to its use.4. Significance and Use4.1 Factors governing selection of a method for the deter-mination of uranium include available quantity of sample,sample purity, desired level of reliability, and equipmentavailability.4.2 This test method determines 20 to 300 mg
19、of uranium,is applicable to fast breeder reactor (FBR)-mixed oxideshaving a uranium to plutonium ratio of 2.5 and greater, istolerant towards most metallic impurity elements usuallyspecified for FBR-mixed oxide fuel, and uses no specialequipment.4.3 The ruggedness of the titration method has been st
20、udiedfor both the volumetric (6) and the weight (7) titration ofuranium with dichromate.5. Interferences5.1 Interfering elements are not generally present in signifi-cant quantities in mixed uranium, plutonium oxide productmaterial. However, elements that cause an error when presentin milligram quan
21、tities are silver (Ag), vanadium (V), pluto-nium (Pt), ruthenium (Ru), osmium (Os), and iodine (I).Interference from tin (Sn), arsenic (As), antimony (Sb), mo-lybdenum (Mo), manganese (Mn), fluorine (F), chlorine (Cl),and bromine (Br) are eliminated when the preparation proce-dure is followed as giv
22、en (4, 8, 9, 10, 11, 12) in this titrimetricmethod. Of the metallic impurity elements usually included inspecifications for FBR-mixed oxide fuel, silver, manganese,lead (Pb), and vanadium interfere.5.2 Other interfering metallic elements are gold (Au), mer-cury (Hg), iridium (Ir), and palladium (Pd)
23、. Elimination oftheir interference requires their separation from uranium bysuch techniques as ion exchange and solvent extraction (13,14).5.3 An initial fuming with sulfuric acid removes suchimpurity elements as the halides and volatile metallic elements.5.4 The effects of impurities and their remo
24、val are listed inTable A1.1 of Annex A1, and the details are given in Refs (4,8, 9, 10, 11, 12, 13, 14, 15).6. Apparatus6.1 BuretPolyethylene bottle (preparation instructionscan be found in Appendix X1), glass weight, or volumetric.6.2 pH Meter, with indicator (platinum has been found to besatisfact
25、ory) and reference (saturated calomel has been foundto be satisfactory) electrodes.NOTE 2The indicator electrode should be changed or cleaned if thereis a titration problem such as less distinct than normal end point break orend point drift, or, if desired, prior to use when more than a week haspass
26、ed since its last use. Suggested cleaning procedures for platinumelectrodes are detailed in Appendix X2.NOTE 3The reference electrode should be covered with a rubber tip orsubmerged in a solution (saturated potassium chloride solution for thecalomel electrode) for overnight storage.7. Reagents7.1 Pu
27、rity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades of reagentsmay be
28、used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean laboratory accepteddemineralized or deionized water
29、.7.3 Ferrous Sulfate (1.0 M)Add 100 mL of sulfuric acid(H2SO4, sp gr 1.84) to 750 mL of water as the solution isstirred. Add 280 g of ferrous sulfate heptahydrate(FeSO47H2O), and dilute the solution to 1 L with water.Prepare ferrous sulfate reagent fresh on a weekly basis. SeeNote 6 on combination o
30、f this reagent.7.4 Nitric Acid (HNO3),8 MAdd 500 mL of HNO3(sp gr1.42) to less than 500 mL of water and dilute to 1 L.7.5 Nitric Acid (8 M)-Sulfamic Acid (0.15 M)-AmmoniumMolybdate (0.4 %)Dissolve4gofammonium molybdate(NH4)6Mo7O244H2O in 400 mL of water, and add 500 mL ofnitric acid (HNO3, sp gr 1.4
31、2). Mix and add 100 mL of 1.5 Msulfamic acid solution (see 7.9) and mix.7.6 Orthophosphoric Acid (H3PO4),85 %Test and treatfor reducing substances prior to use (see Annex A2).7.7 Potassium Dichromate Solution (2 %)Dissolve2gofK2Cr2O7in water, and dilute to 100 g with water.7.8 Potassium Dichromate T
32、itrant (0.0045 M and 0.045M)Dissolve 2.65 g of reagent grade or purer grade K2Cr2O7in water; transfer this solution to a pre-weighed, 2-L volumetricflask and dilute to volume; this solution is for use in titration of20 to less than 100 mg uranium aliquants. Dissolve 26.5 g ofreagent grade or purer g
33、rade K2Cr2O7in water; transfer thissolution to a pre-weighed, 2-L flask and dilute to volume; thissolution is for use in titration of 100 to 300 mg uraniumaliquants.7.8.1 If National Institute of Standards and Technology(NIST) standard reference material dichromate (SRM 136e orequivalent) was used,
34、proceed as in 7.8.1.1 and 7.8.1.2 beforegoing to 7.8.3; otherwise go to 7.8.2.7.8.1.1 Allow the solution to equilibrate to room tempera-ture, weigh the solution, and compute the uranium equivalenttitration factor after correcting the weight of dichromate forbuoyancy (see 11.1.1) and for oxidizing po
35、wer (see 11.1.2).7.8.1.2 Verify the preparation accuracy of the dichromate orceric titrant solution by titration with a standard uraniumsolution (see 7.12) within laboratory accepted error limits.7.8.2 If a reagent grade dichromate or ceric titrant was used,allow the solution to equilibrate to room
36、temperature andstandardize the dichromate solution against CRM uranium (see7.12).7.8.3 Store the dichromate solution in one or more borosili-cate glass bottles with poly-seal tops, or equivalent containers,4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washin
37、gton, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.C 12042to p
38、revent concentration changes due to evaporation.7.9 Sulfamic Acid (1.5 M)Dissolve 146 g of sulfamic acid(NH2SO3H) in water, filter the solution, and dilute to 1 L.7.10 Sulfuric Acid (1 M)Add 56 mL of H2SO4(sp gr 1.84)to water, while stirring, and dilute to 1 L with water.7.11 Sulfuric Acid (0.05 M)A
39、dd 2.8 mL of H2SO4(sp gr1.84) to water, while stirring, and dilute to 1 L with water.7.12 Uranium Reference SolutionGuide C 1128, SectionX3.4 may be used to prepare working reference solutions, orsolutions may be prepared with appropriate in-house proce-dures from certified uranium metal.57.12.1 Cle
40、an the surface of the uranium metal, New Brun-swick Laboratory CRM 112-A or its replacement,5followingthe instructions on the certificate.7.12.2 Weigh the metal by difference to 0.01 mg makingbuoyancy and purity corrections detailed in 11.1.1 and 11.1.2,respectively.7.12.3 Prepare the uranium standa
41、rd solution in accordancewith Guide C 1128 or by the procedure approved for use byyour facility. There are many methods of uranium metaldissolution that are successful; methods that reproduce theuranium assay value on the certificate are acceptable. Anexample of an acceptable dissolution method is g
42、iven inAppendix Appendix X4.7.12.4 Equilibrate the uranium solution to room tempera-ture, and weigh the solution to give the same number ofsignificant figures as the metal weight.7.12.5 Calculate the solution concentration in mg uranium/guranium solution using the calculation in 11.2.2.7.13 Vanadyl
43、Sulfate Dihydrate in Solution (0.0038 Mvanadium(IV)-0.18 M H2SO4)Add 20 mL concentrated sul-furic acid (sp gr 1.84) to less than 980 mL water with stirringand equilibrate to room temperature. Weigh 1.5 g of vanadylsulfate dihydrate (VOSO42H2O) crystals, mix the solid withthe temperature equilibrated
44、 sulfuric acid, and dilute thesolution to 2 L. The vanadyl sulfate concentration shouldprovide 75 to 125 mg VOSO42H2O per titration, but theconcentration is not critical (see Refs (6) and (7).7.13.1 The vanadyl sulfate solution is not stable (16);H2SO4stabilizes the vanadium(IV) oxidation state, but
45、 theH2SO4concentration is not critical. The VOSO42H2O solutionshould be prepared at suitable intervals to prevent vanadi-um(V) interference (24-h intervals for preparation are sug-gested).7.13.2 Alternatively, crystalline vanadyl sulfate dihydrate(75 to 125 mg per titration) may be used with a water
46、 diluentin place of the solution (see 10.13).8. Hazards8.1 Since plutonium- and uranium-bearing materials areradioactive and toxic, adequate laboratory facilities, glovedboxes, fume hoods, etc., along with safe techniques, must beused in handling samples containing these materials. A detaileddiscuss
47、ion of all precautions necessary is beyond the scope ofthis test method. However, personnel who handle radioactivematerials should be familiar with such safe handling practicesas are given in Guide C 852 and Refs (17) and (18).8.2 Committee C-26 Safeguards Statement:8.2.1 The materials (nuclear grad
48、e mixed oxides (U, Pu)O2powders and pellets) to which this test method applies aresubject to nuclear safeguard regulations governing their pos-session and use. The analytical method in this test methodmeets U.S. Department of Energy guidelines for acceptabilityof a measurement method for generation
49、of safeguards ac-countability measurement data.8.2.2 When used in conjunction with the appropriate stan-dard or certified reference materials (SRMs or CRMs), thisprocedure can demonstrate traceability to the national measure-ment base. However, use of this test method does not auto-matically guarantee regulatory acceptance of the resultingsafeguards measurements. It remains the sole responsibility ofthe user of this test method to ensure that its application tosafeguards has the approval of the proper regulatory authori-ties.9. Calibration9.1 If NIST standard po
