1、Designation: C1625 12Standard Test Method forUranium and Plutonium Concentrations and IsotopicAbundances by Thermal Ionization Mass Spectrometry1This standard is issued under the fixed designation C1625; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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 the determination of the con-centration and isotopic composit
3、ion of uranium and plutoniumin solutions. The purified uranium or plutonium from samplesranging from nuclear materials to environmental or bioassaymatrices is loaded onto a mass spectrometric filament. Theisotopic ratio is determined by thermal ionization mass spec-trometry, the concentration is det
4、ermined by isotope dilution.1.2 The values stated in SI units are to be regarded as thestandard. Values in parentheses are for information only.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 standa
5、rd to establish safetyand health practices and determine the applicability of regu-latory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC757 Specification for Nuclear-Grade Plutonium DioxidePowder, Sinterable
6、C776 Specification for Sintered Uranium Dioxide PelletsC833 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsC859 Terminology Relating to Nuclear MaterialsC1008 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsFast Reactor FuelC1068 Guide for Qualification of Measurement
7、Methods bya Laboratory Within the Nuclear IndustryC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC1168 Practice for Preparation and Dissolution of Pluto-nium Materials for AnalysisC1347 Practice for Preparation and Dissolution of Urani
8、umMaterials for AnalysisC1411 Practice for The Ion Exchange Separation of Ura-nium and Plutonium Prior to Isotopic AnalysisC1415 Test Method for238Pu IsotopicAbundance ByAlphaSpectrometryC1614 Practice for the Determination of237Np,232Th,235Uand238U in Urine by Inductively Coupled Plasma-MassSpectro
9、metry (ICP-MS) and Gamma Ray SpectrometryD3084 Practice for Alpha-Particle Spectrometry of Water2.2 Other DocumentsInternational Target Values 2010 for Measurement Uncer-tainties in Safeguarding Nuclear Materials33. Terminology3.1 For definitions of pertinent terms not listed here, seeTerminology C8
10、59.3.2 Definitions of Terms Specific to This Standard:3.2.1 isotope dilution mass spectrometry (IDMS)isotoperatio measurements, using mass spectrometry, of samplesspiked with accurately known weights of individual lowabundance isotopes (adapted from Practice C1614).4. Summary of Test Method4.1 The u
11、ranium and plutonium are separated from eachother and purified from other elements by selective extraction,anion exchange (such as in C1411) or extraction chromatog-raphy. The uranium and plutonium fractions are individuallymounted on filaments of rhenium, tungsten, or tantalum, andare analyzed by t
12、hermal ionization mass spectrometry todetermine the relative abundance of the isotopes. If a known233Uor242Pu (or244Pu) spike is added prior to chemicalseparation the corresponding elemental concentration may alsobe determined by isotope dilution mass spectrometry (IDMS).5. Significance and Use5.1 U
13、ranium and plutonium oxides can be used as a nuclear-reactor fuel in the form of pellets. In order to be suitable for use1This test method is under the jurisdiction of ASTM CommitteeC26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition app
14、roved June 1, 2012. Published July 2012. Originally approvedin 2005. Last previous edition approved in 2005 as C162505. DOI: 10.1520/C1625-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vol
15、ume information, refer to the standards Document Summary page onthe ASTM website.3K. Zhao et. al., “International Target Values 2010 for Measurement Uncertain-ties in Safeguarding Nuclear Materials,” International Atomic Energy AgencySTR-368, 2010.1Copyright ASTM International, 100 Barr Harbor Drive
16、, PO Box C700, West Conshohocken, PA 19428-2959, United States.as a nuclear fuel the starting material must meet certainspecifications, such as found in Specifications C757, C833,C753, C776, C1008, or as specified by the purchaser. Theuranium and/or plutonium concentration and isotopic abun-dances a
17、re measured by mass spectrometry following this testmethod.5.2 The separated heavy element fractions placed on massspectrometric filaments must be very pure. The quantityrequired depends upon the sensitivity of the instrument detec-tion system. If an electron multiplier detector is to be used,only a
18、 few nanograms are required. If a Faraday cup is used, afew micrograms are needed. Chemical purity of the samplebecomes more important as the sample size decreases, becauseion emission of the sample is suppressed by impurities.6. Interferences6.1 Uranium-238 and238Pu interfere in the measurement ofe
19、ach other, and241Am interferes with the measurement of241Pu, thereby requiring chemical separation. Removal ofimpurities provides uniform ionization of uranium or pluto-nium, hence improved precision, and reduces the interferencefrom molecular species of the same mass number as theuranium or plutoni
20、um isotopes being measured. Isotopic analy-sis of plutonium should be completed within a reasonable timeperiod (approximately 20 days) after separation from ameri-cium to minimize interference of241Am ingrowth from241Pu.6.2 Extreme care must be taken to avoid contamination ofthe sample by environmen
21、tal uranium. The level of uraniumcontamination should be measured by analyzing an aliquot of8M nitric acid as a reagent blank and calculating the amount ofuranium it contains.6.3 When238Pu is present in low abundance it may benecessary to measure it by alpha-spectrometry following TestMethod C1415 o
22、r Practice D3084.7. Apparatus7.1 Mass SpectrometerThe suitability of mass spectrom-eters for use with this test method of analysis shall be evaluatedby means of performance tests described in this test method.The mass spectrometer used should possess the followingcharacteristics:7.1.1 A thermal ioni
23、zation source with single or multiplefilaments of rhenium, tungsten or tantalum.7.1.2 An analyzer radius sufficient to resolve adjacentmasses in the mass-to-charge range being studied, that is, m/z= 233 to 238 for U+or 238 to 244 for Pu+. Abundancesensitivity must be great enough to detect one part
24、of236Uin400 parts235U.7.1.3 Aminimum of one stage of magnetic deflection. Sincethe resolution is not affected, the angle of deflection may varywith the instrument design.7.1.4 A mechanism for changing samples.7.1.5 A direct-current (Faraday cup) or electron multiplierdetector, as a single detector s
25、ystem or, several detectors in amulti collector design, followed by a current measuring device.7.1.6 A pumping system to attain a vacuum of less than 400Pa (3 3 10-6torr) in the source, the analyzer, and the detectorregions.7.1.7 A mechanism to scan masses by means of varying themagnetic field or th
26、e accelerating voltage.7.1.8 A computer to collect and process data produced bythe instrument.7.2 An Optical Pyrometer should be available to determinethe filament temperature.7.3 Filament preheating and degassing unit for cleaningunloaded filaments.8. Materials and Reagents8.1 Purity of Reagentsall
27、 reagents used in the finalpurification and filament loading steps should be of the highestpurity available. Other grades may be used if they are deter-mined not to affect the final result.8.2 Filamentshigh purity, the size and configuration areinstrument dependent. Filaments should be degassed, and
28、maybe carbon saturated, prior to use.NOTE 1The purity of the filaments should be confirmed with eachbatch received. Zone refined filaments should be used for low-levelanalyses.8.3 Certified Reference Materials (CRM)of varying iso-topic composition, traceable to a national standard body4, foruse as c
29、alibration and quality control standards.8.4 SpikesMaterials, preferably CRMs, for use in thedetermination of elemental concentration by IDMS.9. Instrument Calibration9.1 The measurement method may be qualified followingGuide C1068 and calibrated following Guide C1156.9.2 The measurement and correct
30、ion for mass discrimina-tion and dead time are critical factors in obtaining precise andaccurate results. Equally critical to the accuracy of the mea-surement is the linearity of the total measuring circuit includingthe collector. Calibration of the mass spectrometer is based onthe assumption that t
31、hese are the only sources of significant (1in 104) systematic error in the measurement. Thus, accuratecalibration is made by analyzing standards of known isotopiccomposition under conditions in which cross-contaminationbetween samples does not occur.9.2.1 For multi-collector systems, the bias betwee
32、n collec-tors may also be an important factor in the systematic error andthus must also be evaluated prior to making measurements.9.2.2 For very low-level samples, or samples with extremeratios, other corrections may need to be made, for example,dark count data/dark current.9.3 Mass DiscriminationUs
33、e a traceable isotopic standardto determine the mass discrimination. The deviation from thecertified value of the 235/238 ratio (for U) or the 239/242 ratio(for Pu) is a measure of the mass discrimination of the massspectrometer.9.3.1 Calculate the elemental mass discrimination bias fac-tor, B, as f
34、ollows:B 5 1/c!aRi/j/Rs!21 (1)where:4Available from USDOE New Brunswick Laboratory, Argonne, IL, or otherequivalent source.C1625 122B = mass discrimination factor,aRi/j= average measured atom ratio of isotope i to isotopejRs= certified atom ratio value of the CRMc = D mass/mass. The values for c for
35、 various ratios andion species include:ratio U+or Pu+235U/238U +3/238236U/235U -1/235233U/238U +5/238234U/235U +1/235242Pu/239Pu -3/239240Pu/239Pu -1/239241Pu/239Pu -2/239238Pu/239Pu +1/2399.3.2 Correct every measured ratio, Ri/j, for mass discrimi-nation as follows:Ri/j5 aRi/j/11cB! (2)where Ri/jis
36、 the corrected atom ratio of isotope i to isotopej9.4 Dead Time CorrectionRequired for counting detec-tors, at high count rates. Use laboratory protocols for thiscorrection with high count rate samples.9.5 LinearityThe linearity of the mass spectrometer maybe determined over the working ratio range
37、by measuringthe235U/238U ratio, under identical conditions, of appropriateCRMs. The ratio of the certified235U/238U ratio to the experi-mental235U/238U ratio is independent of isotopic ratio if thesystem is linear. Under ideal conditions, any deviation from aconstant value greater than 4 in 10,000 i
38、s likely to benonlinearity. Uranium CRMs are used because the range ofisotopic ratios of existing plutonium CRMs is not adequatelylarge.10. Procedure10.1 Sample Preparation10.1.1 Sample DissolutionDissolve an appropriatesample to obtain the desired filament loading for the massspectrometric analysis
39、. See Practice C1347 for the dissolutionof uranium or Practice C1168 for plutonium. Add the appro-priate amount of spike, by weight or volume, as appropriate, ifconcentration is to be determined by isotope dilution methods.NOTE 2Spike addition and equilibration must be performed prior tochemical pur
40、ification if determining concentration by IDMS.10.1.2 Sample PurificationUse Practice C1411 or similarprocedure to separate the uranium and plutonium from eachother and from other impurities.10.2 Filament LoadingSamples may either be directlyloaded by evaporation, electroplated, or loaded onto a res
41、inbead for mounting on the filament. Samples and standardsshould be prepared for analysis by the same method at similarmass loadings.10.3 Sample Heating and Isotopic Ratio Measurement:10.3.1 Insert the filament assembly into the mass spectrom-eter. If the instrument contains a turret to allow loadin
42、g ofseveral samples, load at least one QC sample (blank or CRM)per wheel.10.3.2 Seal the source and evacuate to a pressure of lessthan 400 PA (3 3 10-6torr).10.3.3 Slowly begin heating the sample filament. If not donepreviously, hold the sample filament at a dull, red glow(500-700C) for 5-30 minutes
43、 to permit outgassing (this maybe performed in a separate system to reduce contamination ofthe mass spectrometry source). When outgassing has ceased,increase the ionizing filament temperature to emit ions. Typicalemitting temperatures are 1450-1650C for plutonium and1650-1850C for uranium.10.3.4 Loc
44、ate the uranium or plutonium spike peak,or the238U peak or the239Pu peak, if analyzing unspikedsamples. Focus the major isotope beam by adjusting themagnetic field, the accelerating voltage, and any electrical ormechanical controls available.10.3.5 The intensity of the major beam is adjusted untilst
45、able emission of the desired intensity is achieved. Theemission rate should be constant, or any increase or decreaseshould be slow and even.10.3.6 When acceptable ion emission is reached, measurethe relative intensities of the ion peaks of interest. Multiplemeasurements of isotope pairs are made to
46、provide qualitycontrol parameters.10.3.7 When sufficient data are collected to obtain thedesired precision, turn off the filament current and discontinuethe analysis.10.3.8 Record and correct (see section 9) the isotopic ratiosof the ith to the jth species for the unspiked sample (Ri/j), forthe spik
47、e, (Si/j) and for the sample-plus-spike mixture (Mi/j).The symbols for the isotopes233U,234U,235U,236U,238U,238Pu,239Pu,240Pu,241Pu, and242Pu are abbreviated to 3, 4, 5,6, 8, P8, 9, 0, 1, and 2, respectively (see section 11); note thatthese symbols do not include every isotope that may bemeasured. I
48、n this nomenclature, the observed ratios of238Uto233U in the sample, the spike, and the sample-plus-spikemixture (Ri/j, Si/jand Mi/j) become R8/3, S8/3and M8/3, respec-tively.11. Calculation11.1 Calculate atom fraction235U, A5, on the unspiked U asfollows:A55 R5/8/R4/81 R5/81 R6/81 R8/8! (3)where R8
49、/8(which equals 1) is retained for clarity. Next,calculate atom fraction238U, A8, as follows:A85 R8/8/R4/81 R5/81 R6/81 R8/8! (4)In these equations,238U is assumed to be the principalisotope. For highly enriched U where235U is the principalisotope, obtain the ratio of each isotope to235U instead ofto238U by using R4/5,R5/5,R6/5,R8/5in place of R4/8,R5/8,R6/8, and R8/8. Finally, calculate the atom % N5and N8asfollows:N55 100A5(5)N85 100A8(6)If desired, calculate N4and N6similarly by dividing thecorresponding atom ratio by the same sum of four ratios asC1625
