1、Designation: C1204 14Standard 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
2、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 covers unirradiated uranium-plutoniummixed oxide having a ur
3、anium 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 complete
4、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 obtain
5、ed 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 and plut
6、onium 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 Section 1
7、0.1.3 The values stated 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 ap
8、pro-priate safety and health practices 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 Refere
9、nce Materi-als for Use in Analysis of 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 ur
10、anium, as selected by the facility procedure, 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 phospho
11、ric acid (H3PO4) containingsulfamic acid. The excess 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) titr
12、ant delivered manually on aweight or volume basis is used. The concentration of thechromium(VI) solution is 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
13、beused, providing that the user demonstrates equivalent performance 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
14、90 % of the titrant on a solid massbasis followed by titration to the 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 te
15、st 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, 2014. Published July 2014. Originally approvedin 1991. Last previous edition approved in 2008 as C1204 02 (2008)1.
16、DOI:10.1520/C1204-14.2The boldface numbers in parentheses refer to the list of 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
17、 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 States13.5 The modification of the Davies and Gray titrationmethod, as described originally in Ref (4), may be used insteadof the meth
18、od described 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
19、 modification does not degrade the analysistechnique as stated 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 equipmenta
20、vailability.4.2 This test method is suitable for samples between 20 to300 mg of uranium, is applicable to fast breeder reactor(FBR)-mixed oxides having a uranium to plutonium ratio of2.5 and greater, is tolerant towards most metallic impurityelements usually specified for FBR-mixed oxide fuel, and u
21、sesno special equipment.4.3 The ruggedness of the titration method has been studiedfor 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 produc
22、tmaterial. However, elements that cause bias when present inmilligram quantities are silver (Ag), vanadium (V), plutonium(Pt), ruthenium (Ru), osmium (Os), and iodine (I). Interferencefrom tin (Sn), arsenic (As), antimony (Sb), molybdenum (Mo),manganese (Mn), fluorine (F), chlorine (Cl), and bromine
23、 (Br)are eliminated when the preparation procedure is followed asgiven (4, 8, 9, 10, 11, 12) in this titrimetric method. Of themetallic impurity elements usually included in specificationsfor FBR-mixed oxide fuel, silver, manganese, lead (Pb), andvanadium interfere.5.2 Other interfering metallic ele
24、ments are gold (Au), mer-cury (Hg), iridium (Ir), and palladium (Pd). 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 vol
25、atile metallic elements.5.4 The effects of impurities and their removal 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 instructions canbe found in Appendix X1), glass weight, or volumetric.
26、6.2 pH Meter, with indicator (platinum has been found to besatisfactory) 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 poi
27、nt drift, or, if desired, prior to use when more than a week haspassed 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 soluti
28、on for thecalomel electrode) for overnight storage.7. Reagents7.1 Purity 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 whe
29、resuch specifications are available.4Other grades of reagentsmay be 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 un
30、derstood to mean laboratory accepteddemineralized or deionized water.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
31、 sulfate reagent fresh on a weekly basis. SeeNote 6 on combination of this reagent.7.4 Nitric Acid (HNO3),8MAdd 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)6Mo7O244H2
32、O in 400 mLof water, and add 500 mLofnitric acid (HNO3, sp gr 1.42). 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 %)Dissolve 2 g ofK2Cr2
33、O7in water, and dilute to 100 g with water.7.8 Potassium Dichromate Titrant (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-Lvolumetricflask and dilute to volume; this solution is for use in titration of20 to less than
34、100 mg uranium aliquants. Dissolve 26.5 g ofreagent grade or purer grade 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 potassium dichromate traceable to a national stan-dards la
35、boratory (for example the National Institute of Stan-dards Technology (NIST) in the U.S. or the Federal Institutefor Materials Research and Testing (BAM) in Germany) was4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the test
36、ing 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.C1204 142used, proceed as in 7.8.1.1 and 7.8.1.2
37、 before going to 7.8.3;otherwise go to 7.8.2.7.8.1.1 Allow the solution to equilibrate to roomtemperature, weigh the solution, and compute the uraniumequivalent titration factor after correcting the weight of dichro-mate for buoyancy (see 11.1.1) and for oxidizing power (see11.1.2).7.8.1.2 Verify th
38、e 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 temperature andstandardize the dic
39、hromate 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,to prevent concentration changes due to evaporation.7.9 Sulfamic Acid (1.5 M)Dissolve 146 g of sulfamic acid(NH2SO3H) in water,
40、filter the solution, and dilute to 1 L.7.10 Sulfuric Acid (1 M)Add 56 mLof H2SO4(sp gr 1.84)to water, while stirring, and dilute to 1 L with water.7.11 Sulfuric Acid (0.05 M)Add 2.8 mL of H2SO4(sp gr1.84) to water, while stirring, and dilute to 1 L with water.7.12 Uranium Reference SolutionGuide C11
41、28, 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 Clean the surface of the uranium metal, New Bruns-wick Laboratory CRM 112-A or its replacement,5followingthe instructions on the
42、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 standard solution in accordancewith Guide C1128 or by the procedure approved for use byeach facility. There are many methods of uran
43、ium metaldissolution that are successful; methods that reproduce theuranium assay value on the certificate of analysis for thereference material are acceptable.An example of an acceptabledissolution method is given in Appendix X4.7.12.4 Equilibrate the uranium solution to roomtemperature, and weigh
44、the solution to give the same numberof significant 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 Sulfate Dihydrate in Solution (0.0038 Mvanadium(IV)-0.18 M H2SO4)Add 20 mL concentrated sul-furic ac
45、id (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 sulfuric acid, and dilute thesolution to 2 L. The vanadyl sulfate concentration shouldprovide 75 to
46、 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 theH2SO4concentration is not critical. The VOSO42H2O solutionshould be prepared at suitable interva
47、ls 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 diluentin place of the solution (see 10.13).8. Hazards8.1 Since plutonium- and uranium-bearing mate
48、rials areradioactive and toxic, adequate laboratory facilities, glovedboxes, fume hoods, etc., along with safe techniques, must beused in handling samples containing these materials.Adetaileddiscussion of all precautions necessary is beyond the scope ofthis test method. However, personnel who handle
49、 radioactivematerials should be familiar with such safe handling practicesas are given in Guide C852 and Refs (17) and (18).8.2 Committee C-26 Safeguards Statement:8.2.1 The materials (nuclear grade 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 of safeguards ac-countability measurement data.8.2.2 When used in
