ASTM C1477-2008 Standard Test Method for Isotopic Abundance Analysis of Uranium Hexafluoride and Uranyl Nitrate Solutions by Multi-Collector Inductively Coupled Plasma-Mass Spectro.pdf

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1、Designation: C 1477 08Standard 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 C 1477; the number immediately following the designation i

2、ndicates 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 the isotopic ab

3、undance analysisof234U,235U,236U and238U in samples of hydrolysed uraniumhexafluoride (UF6) by inductively coupled plasma source,multicollector, mass spectrometry (ICP-MC-MS). The methodapplies to material with235U abundance in the range of 0.2 to6 % mass. This test method is also described in ASTMS

4、TP 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 standard to establ

5、ish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofUranium HexafluorideC 787 Specifi

6、cation for Uranium Hexafluoride for Enrich-mentC 996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UD 1193 Specification for Reagent Water2.2 Other Document:STP 1344 Applications of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to Radionuclide Determi-nations33. Terminolo

7、gy3.1 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 of uraniumhexa

8、fluoride (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 detailed inSe

9、ction 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 prepared for measur

10、ement. 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. Thiscalibration solut

11、ion is measured and a mass bias parameter iscalculated that is stored and subsequently imported into each ofthe sample measurements4to correct the measured uraniumisotopic ratios.4.4 Measurements of isotopic ratios in the calibration solu-tion and the subsequent samples are initiated by customisedso

12、ftware. The mass bias factor is computed from the measuredisotopic ratios in the calibration solution. This parameter isthen exported to correct the measured isotopic ratios of thesamples for mass bias. The corrected isotopic abundances are1This test method is under the jurisdiction of ASTM Committe

13、e C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2008. Published August 2008. Originallyapproved in 2000. Last previous edition approved in 2006 as C 1477 06.2For referenced ASTM standards, visit the ASTM website, w

14、ww.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.3Available from ASTM Headquarters.4The uranium isotopic precision of measurement, limit of detection anduncertainty of

15、 measurement are listed in Section 15 and Appendix X1.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.expressed as % atomic and are converted to % mass prior toreporting. Details of the mass bias correction are presented inAppendix X

16、1.5. Significance and Use5.1 The test method is capable of measuring uraniumisotopic abundances of234U,235U,236U and238U as requiredby Specifications C 787 and C 996.6. Interferences6.1 Mass BiasElectrostatic repulsion between uraniumions causes a so-called “mass bias” effect. Mass bias isobserved a

17、s an enhancement in the number of ions detected atthe collectors from the heavier uranium isotopes relative 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 i

18、s specified to be less than 0.5parts per million of the238U ion beam. The method is limitedto the measurement of235U isotopic abundances below 6 %,consequently interference effects with the234U and236U ionbeams are negligible.6.3 Isobaric Molecular InterferencesA molecular inter-ference exists at ma

19、ss 236 between236U and a hydride of235U,which is formed in the plasma. This interference can becorrected by measuring the beam height of the238U hydride atmass 239, and applying the correction defined in Eq 1, to themeasured236U ion beam:5236Uc5236UmS235U 3238UH238UD(1)where:236Uc= the corrected236U

20、 ion beam,236Um= the measured236U ion beam,235U = the measured235U ion beam,238UH = the measured238U hydride 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 a

21、re accentuated when samples that are depletedin235U are measured after enriched samples. Memory effectscan 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 minim

22、ise the background238U ionbeam.6.4.2 A background correction is performed during themeasurement run by 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. Apparatu

23、s7.1 Mass Spectrometer:7.1.1 The mass spectrometer has an inductively coupledplasma (ICP) source and a 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 softwar

24、e and is equipped with an auto-sampler.7.2 Polypropylene Sample Tubes, Screw-Cap,50mL.7.3 Polypropylene Sample Tubes, Screw-Cap,10mL.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

25、to a 1-Lglass storage bottle.8. Reagents and Materials8.1 Purity of WaterDemineralised water as defined byType I of Specification D 1193.8.2 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 i

26、nstrument for multi-collectionmeasurements. The Institute for Reference Materials andMeasurements7(IRMM) 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

27、 areprepared as uranyl nitrate solutions containing 0.4 g/mL ofuranium.8.4 OptionalInternal Reference 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 anin

28、ternal reference to monitor variations in mass bias. The datapresented in this paper was obtained without the use of aninternal reference. However, if the addition of an internalreference is deemed necessary then isotopes of thorium (230and 232) can be used as a suitable internal reference material.

29、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 instrument calibration (mass bias) ar

30、e 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 internal reference material shou

31、ld be preparedwith a dilution appropriate to the sensitivity of the mass5This correction can only be applied to samples which do not contain239Pu (orany other nuclides with mass 239).6The data presented in the paper was obtained using a Nu Plasma massspectrometer, manufactured by Nu Instruments (Nu

32、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 Materials and Measurement, Retieseweg, B-2440 Geel,Belgium.8New Brunswick Laboratory, D-35

33、0, 9800 South CassAvenue,Argonne, Illinois60439.C1477082spectrometer. 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 concentrationof the samples should be adjusted so that the

34、 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 withuranium hexafluoride samples that are taken in the

35、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 proceduresmust be used. A detailed discussion

36、 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 Transfer between 0.2 g and 0.25 g of UF6gas into ag

37、lass 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 Pour the hydrolysed UF6into a 50 mL screw-cappoly

38、propylene 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 transfer to a clean 50 mL screw-cappolypropyle

39、ne 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 using 0.3 M nitric acidsolution, to reduce the ur

40、anic 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 Aqueous Uranyl Nitrate Solutionsof Known Uranic Con

41、centration: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 be mechanically positioned to align with the i

42、on 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 to achieve the configuration shown in Table 1.

43、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 mass range 80 to 238 (achieved using thebeam f

44、rom 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 factor for the UIRMin question is defined in Eq 2:M

45、ass Bias Factor 51235U238Uquoted235U238Umeasured21Dm(2)whereDm = 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 f

46、ound inAppendix X1. As stated in Section 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 ofuraniu

47、m in a 0.3 M nitric acid solution) are held in the9The sample dilutions specified in this section can be varied according toinstrument requirements.10Subsampling of UF6is detailed in ASTM Standard Test Method C 761.TABLE 1Collector L6 L5 L4 IC1 L3 IC0 L2 L1 Ax H1 H2 H3 H4 H5Separation 2U 1U 1U 1U 1U

48、 1U 1U 1U 1U 1U 1U 2U 2UIon Beam230Th232Th 234U235U236U238U238UHwhere: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.C1477083laboratory. Mass bias calibration is an

49、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 of 60 minutes (to allow the system to thermallystabilise),