1、Designation: C 1625 05Standard Test Method forUranium and Plutonium Concentrations and IsotopicAbundances by Thermal Ionization Mass Spectrometry1This standard is issued under the fixed designation C 1625; 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 (e) 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 compo
3、sition 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
4、determined by isotope dilution.1.2 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 safetyand health practices and determine the applicability of regu-latory limitations prior to us
5、e.2. Referenced Documents2.1 ASTM Standards:2C 753 Specification for Nuclear Grade, Sinterable UraniumDioxide PowderC 757 Standard Specification for Nuclear-Grade PlutoniumDioxide Powder, SinterableC 776 Specification for Nuclear Grade, Sinterable UraniumDioxide PelletsC 833 Specification for Sinter
6、ed (Uranium-Plutonium) Di-oxide PelletsC 1008 Standard Specification of Sintered (Uranium-Plutonium) Dioxide Pellets Fast Reactor FuelC 1068 Guide for Qualification of Measurement Methodsby a Laboratory Within the Nuclear IndustryC 1156 Guide for Establishing Calibration for a Measure-ment Method Us
7、ed to Analyze Nuclear Fuel Cycle Mate-rialsC 1168 Practice for Preparation and Dissolution of Pluto-nium Materials for AnalysisC 1347 Practice for Preparation and Dissolution of UraniumMaterials for AnalyisC 1411 Practice for the Ion Exchange Separation of Ura-nium and Plutonium Prior to Isotopic An
8、alysisC 1415 Standard Test Method for238Pu IsotopicAbundanceby Alpha SpectrometryD 3084 Practice for Alpha-Particle Spectrometry of WaterE 137 Practice for Evaluation of Mass Spectrometers forQuantitative Analysis from a Batch Inlet2.2 Other DocumentsInternational Target Values 2000 for Measurement
9、Uncer-tainties in Safeguarding Nuclear Materials33. Summary of Test Method3.1 The uranium and plutonium are separated from eachother and purified from other elements by selective extraction,anion exchange (such as in C 1411) or extraction chromatog-raphy. The uranium and plutonium fractions are indi
10、viduallymounted on rhenium filaments and analyzed by thermalionization mass spectrometry to determine the relative abun-dance of the isotopes. If a known233Uor242Pu (or244Pu) spikeis added prior to chemical separation the corresponding el-emental concentration may also be determined by isotopediluti
11、on mass spectrometry (IDMS).4. Significance and Use4.1 Uranium and plutonium oxides can be used as a nuclear-reactor fuel in the form of pellets. In order to be suitable for useas a nuclear fuel the starting material must meet certainspecifications, such as found in C 757, C 833, C 753, C 776,C 1008
12、, or as specified by the purchaser. The uranium and/orplutonium concentration and isotopic abundances are measuredby mass spectrometry following this test method.4.2 The separated heavy element fractions placed on massspectrometric filaments must be very pure. The quantityrequired depends upon the s
13、ensitivity of the instrument detec-tion system. If an electron multiplier detector is to be used,only a 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 sampl
14、e is suppressed by impurities.1This test 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, 2005. Published October 2005.2For referenced ASTM standards, visit the ASTM w
15、ebsite, 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.3H. Aigner et. al., “International Target Values 2000 for Measurement Uncer-tainties in Safeguarding Nuclear
16、Materials,” International Atomic Energy AgencySTR-327, 2001.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Interferences5.1 Uranium-238 and238Pu interfere in the measurement ofeach other, and241Am interferes with the measurement
17、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 plutonium isotopes being measured. Isotopic analy-sis of pl
18、utonium should be completed within a reasonable timeperiod (approximately 20 days) after separation from ameri-cium to minimize interference of241Am ingrowth from241Pu.5.2 Extreme care must be taken to avoid contamination ofthe sample by environmental uranium. The level of uraniumcontamination shoul
19、d be measured by analyzing an aliquot of8M nitric acid as a reagent blank and calculating the amount ofuranium it contains.5.3 When238Pu is present in low abundance it may benecessary to measure it by alpha-spectrometry followingC 1415 or D 3084.6. Apparatus6.1 Mass SpectrometerThe suitability of ma
20、ss spectrom-eters for use with this test method of analysis shall be evaluatedby means of performance tests described in this test methodand in Practice E 137. The mass spectrometer used shouldpossess the following characteristics:6.1.1 A thermal ionization source with single or multiplefilaments of
21、 rhenium, tungsten or tantalum.6.1.2 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 of236Uin400 parts235U.6.1.3 Aminimum of one stage
22、 of magnetic deflection. Sincethe resolution is not affected, the angle of deflection may varywith the instrument design.6.1.4 A mechanism for changing samples.6.1.5 A direct-current (Faraday cup) or electron multiplierdetector, as a single detector system or, several detectors in amulti collector d
23、esign, followed by a current measuring device.6.1.6 A pumping system to attain a vacuum of less than 400Pa (3 3 10-6torr) in the source, the analyzer, and the detectorregions.6.1.7 A mechanism to scan masses by means of varying themagnetic field or the accelerating voltage.6.1.8 A computer to collec
24、t and process data produced bythe instrument.6.2 An Optical Pyrometer should be available to determinethe filament temperature.6.3 Filament preheating and degassing unit for cleaningunloaded filaments.7. Materials and Reagents7.1 Purity of Reagentsall reagents used in the finalpurification and filam
25、ent loading steps should be of the highestpurity available. Other grades may be used if they are deter-mined not to affect the final result.7.2 Filamentshigh purity, the size and configuration areinstrument dependent. Filaments should be degassed, andmaybe carbon saturated, prior to use.NOTE 1The pu
26、rity of the filaments should be confirmed with eachbatch received. Zone refined filaments should be used for low-levelanalyses.7.3 Certified Reference Materials (CRM)of varying iso-topic composition, traceable to a national standard body4, foruse as calibration and quality control standards.7.4 Spik
27、esMaterials, preferably CRMs, for use in thedetermination of elemental concentration by IDMS.8. Instrument Calibration8.1 The measurement method may be qualified followingC 1068 and calibrated following C 1156.8.2 The measurement and correction for mass discrimina-tion and dead time are critical fac
28、tors 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 these are the only sources of significant (1in 104) systemat
29、ic error in the measurement. Thus, accuratecalibration is made by analyzing standards of known isotopiccomposition under conditions in which cross-contaminationbetween samples does not occur.8.2.1 For multi-collector systems, the bias between collec-tors may also be an important factor in the system
30、atic error andthus must also be evaluated prior to making measurements.8.2.2 For very low-level samples, or samples with extremeratios, other corrections may need to be made, e.g. dark countdata/dark current.8.3 Mass DiscriminationUse a traceable isotopic standardto determine the mass discrimination
31、. 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.8.3.1 Calculate the elemental mass discrimination bias fac-tor, B, as follows:B 5 1/c!aRi/j/Rs!21 (1)where:B = mass discrimination factor,
32、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 various ratios andion species include:4Available from USDOE New Brunswick Laboratory, Argonne, IL, or otherequivalent source.C1625052ratio U+or Pu+235U/238U +3/23
33、8236U/235U -1/235233U/238U +5/238234U/235U +1/235242Pu/239Pu -3/239240Pu/239Pu -1/239241Pu/239Pu -2/239238Pu/239Pu +1/2398.3.2 Correct every measured ratio, Ri/j, for mass discrimi-nation as follows:Ri/j5 aRi/j/11cB! (2)where Ri/jis the corrected atom ratio of isotope i to isotopej8.4 Dead Time Corr
34、ectionRequired for counting detec-tors, at high count rates. Use laboratory protocols for thiscorrection with high count rate samples.8.5 LinearityThe linearity of the mass spectrometer maybe determined over the working ratio range by measuringthe235U/238U ratio, under identical conditions, of appro
35、priateCRMs. 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 is likely to benonlinearity. Uranium CRMs are used because the range
36、ofisotopic ratios of existing plutonium CRMs is not adequatelylarge.9. Procedure9.1 Sample Preparation9.1.1 Sample DissolutionDissolve an appropriate sampleto obtain the desired filament loading for the mass spectromet-ric analysis. See C 1347 for the dissolution of uranium orC 1168 for plutonium.Ad
37、d the appropriate amount of spike, byweight or volume, as appropriate, if concentration is to bedetermined by isotope dilution methods.NOTE 2Spike addition and equilibration must be performed prior tochemical purification if determining concentration by IDMS.9.1.2 Sample PurificationUse C 1411 or si
38、milar proce-dure to separate the uranium and plutonium from each otherand from other impurities.9.2 Filament LoadingSamples may either be directlyloaded by evaporation, electroplated, or loaded onto a resinbead for mounting on the filament. Samples and standardsshould be prepared for analysis by the
39、 same method at similarmass loadings.9.3 Sample Heating and Isotopic Ratio Measurement:9.3.1 Insert the filament assembly into the mass spectrom-eter. If the instrument contains a turret to allow loading ofseveral samples, load at least one QC sample (blank or CRM)per wheel.9.3.2 Seal the source and
40、 evacuate to a pressure of less than400 PA (3 3 10-6torr).9.3.3 Slowly begin heating the sample filament. If not donepreviously, hold the sample filament at a dull, red glow(500-700C) for 5-30 minutes to permit outgassing (this maybe performed in a separate system to reduce contamination ofthe mass
41、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.9.3.4 Locate the uranium or plutonium spike peak,or the238U peak or the239Pu peak, if analyzing unspikedsample
42、s. Focus the major isotope beam by adjusting themagnetic field, the accelerating voltage, and any electrical ormechanical controls available.9.3.5 The intensity of the major beam is adjusted until stableemission of the desired intensity is achieved. The emission rateshould be constant or at least in
43、crease or decrease slowly andevenly.9.3.6 When acceptable ion emission is reached, measure therelative intensities of the ion peaks of interest. Multiplemeasurements of isotope pairs are made to provide qualitycontrol parameters.9.3.7 When sufficient data are collected to obtain the desiredprecision
44、, turn off the filament current and discontinue theanalysis.9.3.8 Record and correct (see section 8) the isotopic ratiosof the ith to the jth species for the unspiked sample (Ri/j), forthe spike, (Si/j) and for the sample-plus-spike mixture (Mi/j).The symbols for the isotopes233U,234U,235U,236U,238U
45、,238Pu,239Pu,240Pu,241Pu, and242Pu are abbreviated to 3, 4, 5,6, 8, P8, 9, 0, 1, and 2, respectively (see section 10); note thatthese symbols do not include every isotope that may bemeasured. In this nomenclature, the observed ratios of238Uto233U in the sample, the spike, and the sample-plus-spikemi
46、xture (Ri/j, Si/jand Mi/j) become R8/3, S8/3and M8/3, respec-tively.10. Calculation10.1 Calculate atom fraction235U, A5, on the unspiked U asfollows:A55 R5/8/R4/81 R5/81 R6/81 R8/8! (3)where R8/8(which equals 1) is retained for clarity. Next,calculate atom fraction238U, A8, as follows:A85 R8/8/R4/81
47、 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
48、 N8asfollows:N55 100A5(5)N85 100A8(6)If desired, calculate N4and N6similarly by dividing thecorresponding atom ratio by the same sum of four ratios asshown in Eq 3 and Eq 4 and by multiplying the resultant atomfraction by 100 to obtain percent as shown in Eq 5 and Eq 6.10.2 Calculate the correspondi
49、ng atom fraction239Pu, A9,and atom percent239Pu, N9, on the unspiked Pu fraction asfollows:A95 R9/9/ R9/91 R0/91 R1/91 R2/9! (7)N95 100A9(8)C1625053where R9/9(which equals 1) is retained for clarity. Ifrequired, include RP8/9determined by either mass spectrometry(this test method) or alpha spectrometry (C 1415). If desired,calculate NP8, N0, N1, and N2similarly by dividing thecorresponding atom ratio by the same sum of four ratios shownin Eq 7 and by multiplying by 100 to obtain percent as shownin Eq 8.10.3 For accountability, it may be necessary to reportis
