ASTM C1672-2007(2014) Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionizatio.pdf

1、Designation: C1672 07 (Reapproved 2014)Standard Test Method forDetermination of Uranium or Plutonium IsotopicComposition or Concentration by the Total EvaporationMethod Using a Thermal Ionization Mass Spectrometer1This standard is issued under the fixed designation C1672; the number immediately foll

2、owing the 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 method desc

3、ribes the determination of the isotopiccomposition and/or the concentration of uranium and pluto-nium as nitrate solutions by the thermal ionization massspectrometric (TIMS) total evaporation method. Purified ura-nium or plutonium nitrate solutions are loaded onto a degassedmetal filament and placed

4、 in the mass spectrometer. Undercomputer control, ion currents are generated by heating of thefilament(s). The ion beams are continually measured until thesample is exhausted. The measured ion currents are integratedover the course of the run, and normalized to a referenceisotope ion current to yiel

5、d isotopic ratios.1.2 In principle, the total evaporation method should yieldisotopic ratios that do not require mass bias correction. Inpractice, some samples may require this bias correction. Whencompared to the conventional TIMS method, the total evapo-ration method is approximately two times fas

6、ter, improvesprecision from two to four fold, and utilizes smaller samplesizes.1.3 The total evaporation method may lead to biases inminor isotope ratios due to peak tailing from adjacent majorisotopes, depending on sample characteristics. The use of anelectron multiplier equipped with an energy fil

7、ter may elimi-nate or diminish peak tailing effects. Measurement of instru-ment abundance sensitivity may be used to ensure that suchbiases are negligible, or may be used to bias correct minorisotope ratios.1.4 This standard does not purport to address all of thesafety concerns, if any, associated w

8、ith its use. It is theresponsibility of the 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:2C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide P

9、owderC757 Specification for Nuclear-Grade Plutonium DioxidePowder, SinterableC776 Specification for Sintered Uranium Dioxide PelletsC787 Specification for Uranium Hexafluoride for Enrich-mentC833 Specification for Sintered (Uranium-Plutonium) Diox-ide PelletsC967 Specification for Uranium Ore Concen

10、trateC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC1008 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsFast Reactor FuelC1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1156 Guide for Establishing Calibration f

11、or a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC1168 Practice for Preparation and Dissolution of PlutoniumMaterials for AnalysisC1347 Practice for Preparation and Dissolution of UraniumMaterials for AnalysisC1411 Practice for The Ion Exchange Separation of Ura-nium and Plutoni

12、um Prior to Isotopic AnalysisC1415 Test Method for238Pu Isotopic Abundance By AlphaSpectrometryD3084 Practice for Alpha-Particle Spectrometry of WaterE137 Practice for Evaluation of Mass Spectrometers forQuantitative Analysis from a Batch Inlet (Withdrawn1992)31This test method is under the jurisdic

13、tion ofASTM 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. Originallyapproved in 2007. Last previous edition approved in 2007 as C167207. DOI:10.1520/C1672-07R14.2For referen

14、ced 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 Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onww

15、w.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 isotopic equilibrationchemical steps performed on amixture of two samples (for example, a uranium sample and auranium spike) to ensure iden

16、tical valency and chemical formprior to purification of the mixture. Failure to perform isotopicequilibration of a sample-spike mixture may result in partialseparation of the sample from the spike during the purificationprocedure, causing a bias in the results of isotope dilution massspectrometry me

17、asurements.3.1.2 abundance sensitivitythe ratio of the measured in-tensity of an ion beam at a mass m to the measured intensityfrom the same isotope measured at one mass difference (forexample, m 6 1). Abundance sensitivity is a measure of themagnitude of peak tailing. Typically measured using urani

18、umat masses 237 and 238.3.2 Acronyms:3.2.1 CRMCertified Reference Materials3.2.2 TIMSThermal Ionization Mass Spectrometry3.2.3 IDMSIsotope Dilution Mass Spectrometry3.2.4 IRMMInstitute for Reference Materials andMeasurements, supplier of Certified Reference Materials, Geel,Belgium3.2.5 NBLNew Brunsw

19、ick Laboratory, supplier of Certi-fied Reference Materials, Argonne, IL, USA4. Summary of Test Method4.1 Typically, uranium and plutonium are separated fromeach other and purified from other elements by selectiveextraction, anion exchange (such as in Practice C1411)orextraction chromatography. The p

20、urified uranium or plutoniumsamples as nitrate solutions are mounted on a degassedrefractory metal filament (typically rhenium, tungsten or tan-talum) and converted to a solid chemical form via controlledheating of the filament under atmospheric conditions. Thefilament is then mounted in the thermal

21、 ionization massspectrometer, in either a single filament or double filamentconfiguration. The filaments are initially heated to yield a smallion beam suitable for lens focusing and peak centering.Following focusing and peak centering, the ion beam intensitydata acquisition begins, with the filament

22、s heated under com-puter control to yield a pre-defined major isotope ion beam ora predefined total intensity for all measured ion beams. Dataacquisition and filament heating continues until the sample isexhausted or the ion beam intensity reaches a pre-defined lowerlimit. Each isotope ion beam inte

23、nsity is integrated over thecourse of the analysis, and the summed intensity for eachisotope is divided by the summed intensity of a commonisotope (typically the most abundant isotope) to yield ratios.The isotopic composition of the sample may be calculated fromthe ratios. Additional information on

24、the total evaporationmethod may be found in Refs (1-4).44.2 The isotope dilution mass spectrometry (IDMS) methodmay be used to determine the uranium or plutonium concen-trations. In this method, a spike of known isotopic compositionand element concentration is added to a sample prior tochemical sepa

25、ration. Typical spike materials include233Uor235U for uranium samples, and239Pu,242Pu or244Pu forplutonium samples. Samples containing both uranium andplutonium (for example, mixed oxide fuels or fuel reprocessingmaterials) may be mixed with a combined U/Pu spike prior toseparation. When using a spi

26、ke containing significant quanti-ties of one or more of the isotopes present in the sample, theisotopic composition of the sample must be known in advance.The spike-sample mixture undergoes a valency adjustment,purification, and is then loaded onto a filament and the isotopiccomposition of the mixtu

27、re is determined. Using the measuredisotope ratios of the spike-sample mixture, the known isotopiccomposition and amount of spike added to the mixture, and theisotopic composition of the sample, the elemental concentra-tion of the sample may be calculated.5. Significance and Use5.1 The total evapora

28、tion method is used to measure theisotopic composition of uranium and plutonium materials, andmay be used to measure the elemental concentrations of thetwo elements when employing the IDMS technique.5.2 Uranium and plutonium compounds are used as nuclearreactor fuels. In order to be suitable for use

29、 as a nuclear fuel thestarting material must meet certain specifications, such asfound in Specifications C757, C833, C753, C776, C787, C967,C996, C1008, or as specified by the purchaser. The uraniumand/or plutonium concentration and isotopic abundances aremeasured by mass spectrometry following this

30、 method.5.3 The total evaporation method allows for a wide range ofsample loading with no loss in precision or accuracy, and isalso suitable for trace-level loadings with consequent loss ofprecision. Typical uranium analyses are conducted usingsample loadings between 10 nanograms and several micro-g

31、rams. Plutonium analyses are generally conducted usingbetween five and 200 nanograms of plutonium per filament.The total evaporation method and modern instrumentationallow for the measurement of minor isotopes using ioncounting detectors, while the major isotopes are simultane-ously measured using F

32、araday cup detectors.5.4 New generations of miniaturized ion counters nowallow extremely small samples, in the picogram to femtogramrange, to be measured via total evaporation methods. Themethod may be employed for measuring environmental orsafeguards inspection samples containing very small quantit

33、iesof uranium or plutonium. Very small loadings require specialsample handling and analysis techniques, and careful evalua-tion of measurement uncertainty contributors.6. Interferences6.1 Ions with atomic masses in the uranium and plutoniumranges cause interference if they have not been removed or i

34、fthey are generated as part of the chemical handling or analysisof the samples. Both238U and238Pu interfere in the measure-ment of each other, and241Am interferes with the measurement4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.C1672 07 (2014)2of241

35、Pu, thereby requiring chemical separation. Removal ofimpurities provides uniform ionization of uranium orplutonium, hence improved precision, and reduces the inter-ference from molecular species of the same mass number as theuranium or plutonium isotopes being measured. Isotopic analy-sis of Plutoni

36、um should be completed within a reasonable timeperiod after separation from Americium to minimize interfer-ence of241Am in-growth from241Pu. An example of a pre-scribed interval limiting the time between sample purificationand isotopic analysis is 20 days. Operators are responsible fordetermining a

37、maximum interval between purification andmass spectrometric analysis, based on an evaluation of241Amin-growth from decaying241Pu and required accuracy andprecision. Other atomic and molecular species may interferewith total evaporation analyses, particularly if they cause achange in the ionization e

38、fficiency of the analyte during ananalysis. Carbon may disturb total evaporation measurements.It is recommended that operators perform validation tests onunique or complex samples by mixing known pure standardswith other constituents to create a matrix-matched standard.6.2 Care must be taken to avoi

39、d contamination of thesample by environmental uranium or traces of plutonium. Thelevel of effort needed to minimize the effect of contaminationof the sample should be based upon the sample size, plannedhandling and processing of the sample, and knowledge of thelevels of contamination present in the

40、laboratory. For verysmall uranium or plutonium samples, extreme care must betaken to ensure that the sample is not contaminated. For thesesamples, residual uranium or plutonium in the mass spectrom-eter and trace uranium in chemicals or the filaments may biasmeasurement data.6.3 The total evaporatio

41、n method may generate biases in theminor isotopes, particularly those isotopes down mass from amajor isotope, such as trace amounts of234U in a highlyenriched235U material, or238Pu in the presence of239Pu.Biases in the minor isotope data occur due to peak tailing fromthe major isotopes. The amount o

42、f peak tailing is a function ofthe design of the instrument and ion beam spread due to sourcedesign and particle collisions in the instrument. The amount ofpeak tailing may be quantified by measuring the abundancesensitivity under identical experimental conditions. A biascorrection may then be appli

43、ed based upon the measuredabundance sensitivity. Additionally, the use of an energy filterplaced before an ion counting detector can greatly reduce peaktailing and allow for accurate measurement of minor isotopes.The use of an energy filter, ultra high-purity filaments andchemicals, effective sample

44、 purification, and low ionizationand evaporation temperatures to minimize238U interferencescan allow for the accurate measurement of small238Pu abun-dances by this technique. Another commonly used methodfor238Pu measurement when in low abundances is the alpha-spectrometry technique, following Test M

45、ethod C1415 orPractice D3084.7. Apparatus7.1 Mass SpectrometerThe suitability of mass spectrom-eters for use with this method of analysis shall be evaluated bymeans of performance tests described in this method and inPractice E137. The mass spectrometer used should possess thefollowing characteristi

46、cs:7.1.1 A thermal ionization source capable of analysis utiliz-ing single and/or double filaments of rhenium; tungsten ortantalum may be substituted with minor modifications in theprocedure.7.1.2 An analyzer radius sufficient to resolve adjacentmasses in the mass-to-charge range being studied, that

47、 is, m/z= 233 to 238 for U+or 238 to 244 for Pu+. Resolution greaterthan 360 (full width at 1 % of peak height) and an abundancesensitivity of less than 10-5. For measuring minor isotopes, anabundance sensitivity as low as achievable is recommended.7.1.3 An instrument capable of monitoring ion beam

48、inten-sity and adjusting filament currents during ion beam integrationis recommended. This eliminates the sample lost betweenintegrations due to the time necessary to adjust the filamentcurrent.7.1.4 A mechanism for changing samples.7.1.5 Multiple direct-current detectors (Faraday cups) or acombinat

49、ion of Faraday cups and electron multiplier detectorin a multi-collector design. Very small samples may bemeasured utilizing a multi-ion counting array.7.1.6 Apumping system to attain a vacuum of less than 400Pa (3 10-6torr) in the source, the analyzer, and the detectorregions. The ability to accurately measure minor isotopes isdirectly related to analyzer pressure. Analyzer pressures belowapproximately 7 Pa (5 10-8torr) are preferable.7.1.7 A mechanism to scan masses by means of varying themagnetic field and the accelerating voltage.7.1.8 A computer to automate instru