1、Designation: C1477 08 (Reapproved 2014)Standard Test Method forIsotopic Abundance Analysis of Uranium Hexafluoride andUranyl Nitrate Solutions by Multi-Collector, InductivelyCoupled Plasma-Mass Spectrometry1This standard is issued under the fixed designation C1477; the number immediately following t
2、he designation indicates the year oforiginal adoption 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
3、 the isotopic abundance analysisof234U,235U,236U and238U in samples of hydrolysed ura-nium hexafluoride (UF6) by inductively coupled plasmasource, multicollector, mass spectrometry (ICP-MC-MS). Themethod applies to material with235U abundance in the range of0.2 to 6 % mass. This test method is also
4、described in ASTMSTP 1344.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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
5、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:2C761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofUranium Hexafluo
6、rideC787 Specification for Uranium Hexafluoride for Enrich-mentC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UD1193 Specification for Reagent Water2.2 Other Document:STP 1344 Applications of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to Radionuclide Determi-nation
7、s33. Terminology3.1 Acronyms:3.1.1 amuatomic mass unit3.1.2 ICP-MC-MSInductively Coupled Plasma Multi-Collector Mass Spectrometer3.1.3 ICP-MSInductively Coupled Plasma Mass Spec-trometer3.1.4 UIRMUranium Isotopic Reference Material4. Summary of Test Method4.1 Samples are received either in the form
8、of uraniumhexafluoride (UF6) or aqueous uranic solution. The UF6samples are hydrolysed, diluted and acidified with nitric acid.Uranic solution samples are diluted and acidified with nitricacid. If required, an internal reference of thorium isotopes canbe subsequently added to each diluted sample. As
9、 detailed inSection 8, isotope pairs of elements other than thorium couldbe used for an internal reference.4.2 The samples are contained in polypropylene tubes thatare inserted into the auto-sampler rack of the mass spectrom-eter. Sample details are input to the computer and the instru-ment is prepa
10、red for measurement. The automatic measuringsequence is initiated.4.3 Uranium Isotopic Reference Materials (UIRMs) areused to calibrate the instrument. Each UIRM is prepared inaqueous solution (acidified with nitric acid) and if requiredspiked with the same internal reference as the samples. Thiscal
11、ibration solution is measured and a mass bias parameter is1This 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. 1, 2014. Published February 2014. Originallyapprove
12、d in 2000. Last previous edition approved in 2008 as C1477 08. DOI:10.1520/C1477-08R14.2For 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 to the standards Document Summar
13、y page onthe ASTM website.3Available from ASTM Headquarters.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1calculated that is stored and subsequently imported into each ofthe sample measurements4to correct the measured uraniumisotopi
14、c ratios.4.4 Measurements of isotopic ratios in the calibration solu-tion and the subsequent samples are initiated by customisedsoftware. The mass bias factor is computed from the measuredisotopic ratios in the calibration solution. This parameter isthen exported to correct the measured isotopic rat
15、ios of thesamples for mass bias. The corrected isotopic abundances areexpressed as % atomic and are converted to % mass prior toreporting. Details of the mass bias correction are presented inAppendix X1.5. Significance and Use5.1 The test method is capable of measuring uraniumisotopic abundances of2
16、34U,235U,236U and238U as requiredby Specifications C787 and C996.6. Interferences6.1 Mass BiasElectrostatic repulsion between uraniumions causes a so-called “mass bias” effect. Mass bias isobserved as an enhancement in the number of ions detected atthe collectors from the heavier uranium isotopes re
17、lative to thelighter uranium isotopes. A calibration procedure is used tocorrect the mass spectrometer for mass bias.6.2 Adjacent Isotopic PeaksThe abundance sensitivity ofthe ICP-MC-MS at mass 237 is specified to be less than 0.5parts per million of the238U ion beam. The method is limitedto the mea
18、surement of235U isotopic abundances below 6 %,consequently interference effects with the234U and236U ionbeams are negligible.6.3 Isobaric Molecular InterferencesAmolecular interfer-ence exists at mass 236 between236U and a hydride of235U,which is formed in the plasma. This interference can becorrect
19、ed by measuring the beam height of the238U hydride atmass 239, and applying the correction defined in Eq 1,tothemeasured236U ion beam:5236Uc5236Um2S235U 3238UH238UD(1)where:236Uc= the corrected236U ion beam,236Um= the measured236U ion beam,235U = the measured235U ion beam,238UH = the measured238U hy
20、dride ion beam, and238U = the measured238U ion beam.6.4 Memory Effects:6.4.1 Contamination of the sample introduction systemfrom previous samples produces memory interference effects.Such effects are accentuated when samples that are depletedin235U are measured after enriched samples. Memory effects
21、can be readily assessed by aspirating a 0.3 M nitric acidsolution and measuring the background238U ion beam. Thesample introduction system should be periodically disas-sembled and cleaned, to minimise the background238U ionbeam.6.4.2 A background correction is performed during themeasurement run by
22、monitoring the analyte signals of the 0.3M nitric acid rinse solution. The background correction ismeasured prior to the mass calibration and is re-measuredbefore each subsequent sample.7. Apparatus7.1 Mass Spectrometer:7.1.1 The mass spectrometer has an inductively coupledplasma (ICP) source and a
23、double focusing electrostatic/magnetic sector analyser equipped with twelve Faraday detec-tors and two ion counters.67.1.2 The mass spectrometer is fully computer controlledusing customised software and is equipped with an auto-sampler.7.2 Polypropylene Sample Tubes, Screw-Cap, 50 mL.7.3 Polypropyle
24、ne Sample Tubes, Screw-Cap, 10 mL.7.4 Positive Displacement Pipette, and Tips to Suit, 0.01mL.7.5 Positive Displacement Pipette, and Tips to Suit, 1 mL.7.6 Variable-Volume Dispenser, 1 to 5 mL, fitted to a 1-Lglass storage bottle.8. Reagents and Materials8.1 Purity of WaterDemineralised water as def
25、ined byType I of Specification D1193.8.2 High Purity 0.3 M Nitric Acid Solution (x 50 dilutionof the concentrated acid).8.3 Uranium Isotopic Reference Material (UIRMs)UIRMs are used to calibrate the instrument for multi-collectionmeasurements. The Institute for Reference Materials andMeasurements7(I
26、RMM) reference material IRMM-024 is usedfor enriched samples and the New Brunswick Laboratory8Certified Reference Material CRM U005-Ais used for samplesof natural or depleted235U abundances. The UIRMs areprepared as uranyl nitrate solutions containing 0.4 g/mL ofuranium.8.4 OptionalInternal Referenc
27、e Solution containing230Thand232Th isotopes (or isotopes of another suitable element).8.4.1 It has been found that the stability of the modernICP-MC-MS can be such that it is not necessary to use aninternal reference to monitor variations in mass bias. The datapresented in this paper was obtained wi
28、thout the use of an4The uranium isotopic precision of measurement, limit of detection anduncertainty of measurement are listed in Section 15 and Appendix X1.5This correction can only be applied to samples which do not contain239Pu (orany other nuclides with mass 239).6The data presented in the paper
29、 was obtained using a Nu Plasma massspectrometer, manufactured by Nu Instruments (Nu Instruments Ltd, Unit 74Clywedog Road South, Wrexham LL13 9XS, North Wales, UK). The Nu Plasmawas supplied with the (optional) BIG80 vacuum pumping system to achieveoptimum sensitivity.7Institute for Reference Mater
30、ials and Measurement, Retieseweg, B-2440 Geel,Belgium.8New Brunswick Laboratory, D-350, 9800 South CassAvenue,Argonne, Illinois60439.C1477 08 (2014)2internal reference. However, if the addition of an internalreference is deemed necessary then isotopes of thorium (230and 232) can be used as a suitabl
31、e internal reference material.The internal reference must contain at least one pair of isotopesin a fixed ratio. It is not necessary for this isotopic ratio to beaccurately known as the same reference is added to both thecalibration material and the subsequent samples. Minor fluc-tuations in instrum
32、ent calibration (mass bias) are reflected inthe measured ratio of the internal reference in the samples.Subsequent correction of the mass bias parameter using themeasured ratio of the internal reference provides the necessaryadjustment to the mass bias factor prior to result calculation.8.4.2 The in
33、ternal reference material should be preparedwith a dilution appropriate to the sensitivity of the massspectrometer. If thorium is used as the internal reference thena thorium to uranium ratio of approximately 1:2 should beadequate.NOTE 1If an internal reference is added, then the uranic concentratio
34、nof the samples should be adjusted so that the uranic concentration requiredfor the mass spectrometer is achieved following the addition of theinternal reference.NOTE 2The decay of234Uto230Th may present a problem with theanalysis of aged-uranic solutions. This should not present a problem withurani
35、um hexafluoride samples that are taken in the gaseous phase, asgaseous UF6separates from any non-volatile thorium compounds.9. Hazards9.1 A number of the materials used in this procedure areradioactive, toxic, corrosive or any combination of the three.Adequate laboratory facilities and safe handling
36、 proceduresmust be used. A detailed discussion of all safety procedures isbeyond the scope of this method. Site specific practices for thehandling of radioactive materials and hazardous chemicalsshould be followed.10. Sampling, Test Specimens, and Test Units910.1 Samples Received as UF6:10.1.1 Trans
37、fer between 0.2 g and 0.25 g of UF6gas into aglass sample tube cooled by liquid nitrogen.1010.1.2 Working in a fume cupboard, hydrolyse the UF6using demineralised water from a wash bottle. The operatorshould keep the sample tube pointed away at all times sincesome toxic HF gas is produced.10.1.3 Pou
38、r the hydrolysed UF6into a 50 mL screw-cappolypropylene tube and dilute so that the final concentration ofUF6is 5 mg/mL. For example, if the weight of UF6transferredis 0.2 g, dilute to 40 mL with demineralised water.10.1.4 Using a positive displacement pipette, take a 0.01mL aliquot of solution and
39、transfer to a clean 50 mL screw-cappolypropylene tube. Dilute to a volume of 42 mL using a 0.3 Mnitric acid solution. The resulting solution contains 1.2 g/mLof UF6which is equivalent to 0.8 g/mL of uranium.10.1.5 Pour 2 mL of solution into a 10 mL polypropylenetube and double the volume to 4 mL usi
40、ng 0.3 M nitric acidsolution, to reduce the uranic concentration to 0.4 g/mL.10.1.6 If required, add an aliquot of the thorium internalreference and mix the solution thoroughly (see 8.4).10.1.7 Place the tube in the designated rack position inaccordance with Section 13.10.2 Samples Received as Aqueo
41、us Uranyl Nitrate Solutionsof Known Uranic Concentration:10.2.1 Dilute the sample with a 0.3 M nitric acid solution sothat the uranium concentration is 0.8 g/mL.10.2.2 Proceed in accordance with 10.1.5 10.1.7.11. Preparation of Apparatus11.1 Many ICP-MC-MS designs require the Faraday collec-tors to
42、be mechanically positioned to align with the ion beams.The instrument used for this work adopts a different approach,where a “zoom lens” which alters the dispersion of theinstrument is used to focus the beams onto a fixed array ofdetectors. The zoom lens settings were adjusted under softwarecontrol
43、to achieve the configuration shown in Table 1.11.2 To minimise measurement uncertainty, minor isotope(234U and236U) abundances are measured with ion counters.The analyser magnet must be calibrated across the mass range230 to 238, however, the instrument manufacturer recommendscalibrating across the
44、mass range 80 to 238 (achieved using thebeam from the Argon dimer). The magnet should be re-calibrated if the calibration drifts by more than 0.2 atomic massunits.12. Calibration and Standardization12.1 Calibration of the mass spectrometer using a UIRMproduces a mass bias factor. The mass bias facto
45、r for the UIRMin question is defined in Eq 2:9The sample dilutions specified in this section can be varied according toinstrument requirements.10Subsampling of UF6is detailed in ASTM Standard Test Method C761.TABLE 1Collector L6 L5 L4 IC1 L3 IC0 L2 L1 Ax H1 H2 H3 H4 H5Separation 2U 1U 1U 1U 1U 1U 1U
46、 1U 1U 1U 1U 2U 2UIonBeam230Th232Th 234U235U236U238U238UH where:Ax = Axial Faraday collector,L and H = low and high mass Faraday collectors (with respect to the Axial collector),IC = ion counters, andU = unit mass dispersion for uranium isotopes.C1477 08 (2014)3Mass Bias Factor 51235U238Uquoted235U2
47、38Umeasured21m(2)wherem = ratio mass difference (that is, 3 in the case ofthe235U/238U ratio).12.2 The mass bias factor is exported to all subsequentsample measurements to correct for mass bias effects. Detailsof how the mass bias correction is applied can be found inAppendix X1. As stated in Sectio
48、n 8, IRMM-024 is used tocalibrate for mass bias for samples enriched in235U and NBLCRM 005-A is used to calibrate for mass bias for naturalsamples or samples depleted in235U. Stock solutions of boththese uranium reference materials (containing 0.4 g/mL ofuranium in a 0.3 M nitric acid solution) are
49、held in thelaboratory. Mass bias calibration is an integral part of eachsample run (that is, no separate calibration procedure isnecessary).13. Procedure13.1 The instrument software is used to assign samplenames, measurement procedures and auto-sampler rack posi-tions to both UIRMs and samples. Two sample racks are used.The first rack contains the UIRM IRMM-024 and thosesamples that are enriched in235U. The second rack contains theUIRM NBL CRM U005-A and those samples at natural levelor depleted in235U. The plasma is then struck and after aperiod o
