1、Designation: C 1206 02Standard Test Method forPlutonium by Iron (II)/Chromium (VI) AmperometricTitration1This standard is issued under the fixed designation C 1206; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. 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 the determination of plutoniumin unirradiated nuclear-grade plutonium dioxide, uranium-plutonium mi
3、xed oxides with uranium (U)/plutonium (Pu)ratios up to 21, plutonium metal, and plutonium nitratesolutions. Optimum quantities of plutonium to measure are 7 to15 mg.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of th
4、e user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 1168 Practice for Preparation and Dissolution of Pluto-nium Materials for Analysis23. Committee C-26 Safeg
5、uards Statement3.1 The materials nuclear-grade mixed oxides (U, Pu)O2powders, pellets, Pu metal, Pu oxides, and Pu nitrates to whichthis test method applies, are subject to nuclear safeguardsregulations governing their possession and use. This analyticaltest method has been designated as technically
6、 acceptable forgenerating safeguards accountability measurement data forplutonium.3.2 When used in conjunction with appropriate standardreference material this test method can demonstrate traceabilityto the national measurement base. However, adherence to thistest method does not automatically guara
7、ntee regulatory accep-tance of the resulting safeguards measurements. It remains thesole responsibility of the user of this test method to ensure thatits application to safeguards has the approval of the properregulatory authorities.4. Summary of Test Method4.1 Amperometric titrations are based on t
8、he measuredchange in the current flow between two electrodes, held atconstant potential, when a titrant is added. The plutonium isfirst oxidized to the +6 oxidation state in a dilute sulfuric acidsolution with argentic oxide. The excess oxidant is destroyedby heating, and the Pu(VI) is then reduced
9、to Pu(IV) by excessFe(II) during the titration. The excess Fe(II) is titrated byCr(VI), and the Pu determined by difference from the quanti-ties of the two titrants.4.2 Oxide and metal samples are prepared to produce finalsolutions as a soluble sulfate. Plutonium-nitrate solutions canbe introduced d
10、irectly at the beginning of the procedure and arelater diluted with sulfuric acid. Chlorides must be removed.5. Significance and Use5.1 All plutonium materials covered in this test method areused in the preparation of nuclear-reactor fuels. In order to besuitable for this purpose, the materials must
11、 meet specifiedcriteria for plutonium content. This test method is used toverify the plutonium content.5.2 A primary standard dichromate such as that availablefrom National Institute of Standards and Technology (NIST) ora dichromate traceable to a primary standard such as NewBrunswick Laboratory (NB
12、L) plutonium standard, is requiredfor this technique.6. Interferences6.1 Interference is caused by ions that are oxidized byargentic oxide and reduced by ferrous ion in sulfuric-acidsolution. Elements that may be present in plutonium materialsand that will produce quantitative positive errors includ
13、evanadium (V), chromium (Cr), and manganese (Mn). Correc-tion can be made for these elements by calculation when theydo not individually exceed 200 g impurity elements per gramof plutonium.6.2 Other elements that will cause positive errors includecerium (Ce), ruthenium (Ru), gold (Au), rhodium (Rh),
14、 plati-num (Pt), lead (Pb), and neptunium (Np). Americium (Am)does not interfere because it is not oxidized to higher valencystates during the argentic oxidation.6.3 Thallium (Tl), selenium (Se), calcium (Ca), and barium1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel
15、 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 120691. Last previous edition C 120691(1996).2Annual Book of ASTM Standards, Vol 12.01.1Copyright ASTM International, 100 Barr Harbo
16、r Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(Ba) give low results.7. Apparatus7.1 Weighing Burets, polyethylene drop-dispenser bottleswith polypropylene dropping closure and cap, 30 and 60-mLsizes.3Squeeze deliveries are made with these burets. They areplaced in a secondary
17、, cut-off, slightly larger diameter polyeth-ylene bottle to prevent mass changes from contact with thehands. Burets are transferred to and from the balance usingforceps.7.2 Digital Voltmeter, d-c precision, readable to 0.2 mv.47.3 Microelectrode, rotating platinum.57.4 Reference Mercury Electrode, s
18、aturated mercurous sul-fate.67.5 Titrator/Detector, amperometric (see Fig. 1).8. Reagents8.1 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 Am
19、erican Chemical Society wheresuch specifications are available.7Other grades may be used,provided it is first ascertained that the reagent is of sufficienthigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Purity of WaterUnless otherwise indicated, referencesto wate
20、r shall be understood to mean deionized or distilledwater.8.3 Argentic Oxide (AgO).8.4 Ferrous Ammonium Sulfate Solution, Iron (II) TitrantDissolve 19.6 g of Fe(NH4)2(SO4)26 H2O in 500 mL of cold1 N H2SO4and dilute to 1 L with 1 N H2SO4. The solution isstandardized daily or before beginning a series
21、 of plutoniumstandard and sample titrations, or both.8.5 Potassium Dichromate SolutionUse NIST SRM136e8or equivalent. Weigh approximately 4.9 g to nearest0.0001 g of potassium dichromate (K2Cr2O7) and dissolve inwater. Transfer to a tared 2-L volumetric flask. Dilute tovolume with water. Weigh the f
22、lask and contents. Make thebuoyancy correction and determine the mass of the solution.Express the oxidizing strength as milliequivalents per gram ofsolution (C1).C1 5K 3 P 3 BE 3 S(1)where:C1=K2Cr2O7concentration, milliequivalents per gram,K = weight, mg, K2Cr2O7,P = purity of K2Cr2O7,B = buoyancy c
23、orrection for K2Cr2O7, 1.00031 (use onlyif significant),E = equivalent weight of K2Cr2O7, 49.0320, andS = weight of solution, g.8.6 Sulfuric Acid (0.5 N)Prepare by adding 14 mL ofsulfuric acid (H2SO4, sp gr 1.84) to water with stirring anddilute to 1 L.8.7 Sulfuric Acid (1 N)Prepare by adding 28 mL
24、ofH2SO4(sp gr 1.84) to water with stirring and dilute to 1 L.8.8 Sulfuric Acid (18 N)Prepare by carefully adding(with continuous stirring) 500 mL of H2SO4(sp gr 1.84) slowlyto 450 mL water, cool, and dilute to 1 L.9. Standardization of Iron (II) Titrant9.1 Transfer 20 mL water and 10 mL of 18 N H2SO
25、4to aclean 50-mL beaker. Add a small stirring bar.9.2 Place the beaker under the electrode assembly andsupport the beaker with a small magnetic stirrer so that theelectrodes are immersed near the center. Start the rotation ofthe platinum electrode and turn on the magnetic stirrer.NOTE 1Some magnetic
26、 stirrers will cause digital voltmeter instabilitypossibly due to a bad ground. The titration may be run with such a stirrerif it is turned off just before each current reading.3Nalgene drop-dispenser bottles, Nos. 2411-0030 and 2411-0060 have beenfound satisfactory.4Both Ealing Pye Scalamp Microamm
27、eter No. 29-222 and Keithley Model 197Digital Multimeter have been found satisfactory.5Both Sargent refer to Section 11, Calculation). For plutonium nitrate solu-tions, proceed to 10.2; otherwise proceed to 10.3.10.2 Plutonium Nitrate Sample PreparationTransfer ali-quants (150 to 350 mg Pu) of pluto
28、nium nitrate solutiondirectly into a 30-mL tared weighing buret (BO) and reweigh(S1). Add 1.0 N H2SO4to obtain a final Pu concentration of 5to 12 mg/g of solution and reweigh the buret (B1). The originalsample aliquant and dilution are made in the same buret. Sincethe transfer to the weighing buret
29、has been made, proceed to10.4.10.3 Transfer the solution of the sample to tared (60.1 mg)60-mL weighing buret (BO). Rinse the dissolution containerseveral times with 0.5 N H2SO4to complete the transfer.Replace cap and reweigh (B1) to nearest 0.1 mg.10.4 Transfer by weight an aliquant of sample (B2B3
30、) tocontain 7 to 15 mg Pu to a 50-mL beaker.10.4.1 For solutions containing HCl and samples dissolvedby acid or sealed tube dissolution add 3 drops 18 N H2SO4(spgr 1.84) and heat to fumes on hot plate. When fuming ceases,remove from hot plate (Do not bake.). Cool. This step is notrequired for soluti
31、ons not containing HCl.10.4.2 Add 10 mL 0.5 N H2SO4.10.5 Add approximately 50 mg of AgO to the solution.Gently swirl the beaker. Let stand for 30 min with occasionalswirling. Perform the procedure described in Section 9, Stan-dardization of Titrant, while waiting.10.5.1 Incomplete oxidation of the p
32、lutonium can occur athigh sulfuric acid concentrations. The presence of an excess ofoxidant is shown by a characteristic blackish-brown color or ablack precipitate. If the dark color does not persist, add moreAgO in 10-mg increments to complete the oxidation.10.6 Add 1 N H2SO4to bring the total volu
33、me to about 20mL. Rinse the sides of the beaker while adding the acid. Heat(+80C) to destroy excess black AgO. Cool to less than 40C.Add a small stirring bar.10.7 Place the beaker under the electrode assembly andsupport with a small magnetic stirrer so that the electrodes areimmersed near the center
34、. Start the rotation of the platinumelectrode and turn on the magnetic stirrer. (See 10.5.1.)10.8 Slowly add 10 mL of 18 N H2SO4while washing theinner surface of the beaker with the acid.10.9 Turn on the digital voltmeter and amperometric end-point detector. Turn the detector I/E switch to the “E” (
35、poten-tial) position.10.10 Adjust the potential to 600 mV, then turn the I/Eswitch to “I” (current) and observe and record the residualcurrent (A0). The residual current should be less than 0.2 A.NOTE 2A persistent higher residual current (0.2 A) indicates thepresence of interfering ions which are b
36、eing oxidized at the platinumelectrode.10.11 Tare weigh the dichromate (D1) and the standardizediron (F1) solution weighing burets.10.12 Slowly add, dropwise, increments of the standardizediron solution until a current of 10 to 15 A is attained. Reweighthe iron solution weighing buret (F2).10.13 Slo
37、wly backtitrate the excess iron (II) with standardpotassium dichromate solution to a current reading of 5 to 10A. Reweigh the dichromate solution weighing buret (D2) andrecord the current (A1) reading.10.14 Carefully add more dichromate until a current readingof 1 to 3 A is attained. Reweigh the dic
38、hromate solutionweighing buret (D3) and record the current (A2) reading.10.15 Calculate the sample result as described in Section 11.10.16 Remove the electrodes from the titration solution,rinse the electrodes thoroughly with 1 N H2SO4, and then rinsethe electrodes with deionized water. The apparatu
39、s is nowready for the next sample.11. Calculation11.1 Calculate plutonium content and ferrous standardiza-tion as follows:11.1.1 Ferrous Standardization:CO, meq/g 5FD1D3! 1A2A0!D2D3!A1A2!GC1F1F2!(2)C 1206311.1.2 Solid Samples:FF1F2! CO2FD1D3! 1A2A0! D2D3!A1A2!GC1GPu, % 5WB1B0!#100G1G0! B2B3! 1000! 2
40、!(3)11.1.3 Solution Samples:FF1F2! CO2FD1D3! 1A2A0! D2D3!A1A2!GC1GPu/g solution, mg 5WB1B0!#S1B0! B2B3! 2!(4)where:F1 = first ferrous ammonium sulfate buret weight, g,F2 = second ferrous ammonium sulfate buret weight,g,C0 = concentration of ferrous ammonium sulfate solu-tion, milliequivalents per gr
41、am of solution,D1 = first potassium dichromate solution buret weight,g,D2 = second potassium dichromate solution buretweight, g,D3 = third potassium dichromate solution buretweight, g,A0 = residual current,A1 = first ammeter reading,A2 = second ammeter reading,C1 = concentration of potassium dichrom
42、ate solution,milliequivalents per gram of solution,W = atomic weight of plutonium in sample (see Note3),B0 = empty sample/dilution buret weight, g,B1 = full sample buret weight, g,B2 = sample buret weight before dispensing aliquant,g,B3 = sample buret weight after dispensing aliquant, g,G1G0 = net w
43、eight of solid samples, g,S1 = weight of sample/dilution buret plus sample, g.NOTE 3Adjust atomic weight for isotopic composition.12. Precision and Bias912.1 The precision (relative standard deviation) of themethod is 0.1 % based on 64 measurements from 5 separatemixed oxide solutions of the same Sa
44、feguards AnalyticalLaboratory Evaluation (SALE) Program standard taken over a12-month period in a single laboratory.12.2 Based on the same measurements there was no statis-tically significant bias.13. Keywords13.1 amperometric; plutonium analysis; plutonium-uranimmixed oxides (MOX)ASTM International
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48、t the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).9Supporting data are available from ASTM Headquarters. Request RR: C26-1003.C 12064
