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

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1、Designation: C 1672 07Standard 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 C 1672; the number immediately following the design

2、ation 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This method describes the deter

3、mination 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 in the mass sp

4、ectrometer. 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 yield isotopic rati

5、os.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 faster, improvespr

6、ecision 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 filter may elimi-n

7、ate 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 with its use. It

8、 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:2C 753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC 757 Spe

9、cification for Nuclear-Grade Plutonium DioxidePowder, SinterableC 776 Specification for Sintered Uranium Dioxide PelletsC 787 Specification for Uranium Hexafluoride for Enrich-mentC 833 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsC 967 Specification for Uranium Ore ConcentrateC 99

10、6 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC 1008 Specification for Sintered (Uranium-Plutonium) Di-oxide PelletsFast Reactor FuelC 1068 Guide for Qualification of Measurement Methodsby a Laboratory Within the Nuclear IndustryC 1156 Guide for Establishing Calibration for a

11、Measure-ment Method Used 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 AnalysisC 1411 Practice for The Ion Exchange Separation of Ura-nium and Plutoni

12、um Prior to Isotopic AnalysisC 1415 Test Method for238Pu Isotopic Abundance ByAlpha SpectrometryD 3084 Practice for Alpha-Particle Spectrometry of WaterE 137 Practice for Evaluation of Mass Spectrometers forQuantitative Analysis from a Batch Inlet31This test method is under the jurisdiction of ASTM

13、Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2007. Published July 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual

14、 Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 Definitions:3.1.1 isotopic equilibrationchemical

15、steps performed on amixture of two samples (for example, a uranium sample and auranium spike) to ensure identical 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 s

16、pike during the purificationprocedure, causing a bias in the results of isotope dilution massspectrometry measurements.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

17、, m 6 1). Abundance sensitivity is a measure of themagnitude of peak tailing. Typically measured using uraniumat 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 Ref

18、erence Materials and Mea-surements, supplier of Certified Reference Materials, Geel,Belgium3.2.5 NBLNew Brunswick 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

19、 elements by selectiveextraction, anion exchange (such as in Practice C 1411)orextraction chromatography. The purified 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

20、 via controlledheating of the filament under atmospheric conditions. Thefilament is then mounted in the thermal 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 ce

21、ntering.Following focusing and peak centering, the ion beam intensitydata acquisition begins, with the filaments 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 unti

22、l the sample isexhausted or the ion beam intensity reaches a pre-defined lowerlimit. Each isotope ion beam intensity 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 y

23、ield ratios.The isotopic composition of the sample may be calculated fromthe ratios. Additional information on 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 me

24、thod, a spike of known isotopic compositionand element concentration is added to a sample prior tochemical separation. Typical spike materials include233Uor235U for uranium samples, and239Pu,242Pu or244Pu forplutonium samples. Samples containing both uranium andplutonium (for example, mixed oxide fu

25、els or fuel reprocessingmaterials) may be mixed with a combined U/Pu spike prior toseparation. When using a spike 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

26、 a valency adjustment,purification, and is then loaded onto a filament and the isotopiccomposition of the mixture 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 sa

27、mple, the elemental concentra-tion of the sample may be calculated.5. Significance and Use5.1 The total evaporation 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

28、technique.5.2 Uranium and plutonium compounds are used as nuclearreactor fuels. In order to be suitable for use as a nuclear fuel thestarting material must meet certain specifications, such asfound in Specifications C 757, C 833, C 753, C 776, C 787,C 967, C 996, C 1008, or as specified by the purch

29、aser. Theuranium and/or plutonium concentration and isotopic abun-dances are measured by mass spectrometry following thismethod.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 consequen

30、t loss ofprecision. Typical uranium analyses are conducted usingsample loadings between 10 nanograms and several micro-grams. Plutonium analyses are generally conducted usingbetween five and 200 nanograms of plutonium per filament.The total evaporation method and modern instrumentationallow for the

31、measurement of minor isotopes using ioncounting detectors, while the major isotopes are simulta-neously measured using Faraday 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 meth

32、ods. Themethod may be employed for measuring environmental orsafeguards inspection samples containing very small quantitiesof uranium or plutonium. Very small loadings require specialsample handling and analysis techniques, and careful evalua-tion of measurement uncertainty contributors.6. Interfere

33、nces6.1 Ions with atomic masses in the uranium and plutoniumranges cause interference if they have not been removed or ifthey 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 measurem

34、entof241Pu, thereby requiring chemical separation. Removal ofimpurities provides uniform ionization of uranium or pluto-nium, hence improved precision, and reduces the interference4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.C1672072from molecular s

35、pecies of the same mass number as theuranium or plutonium isotopes being measured. Isotopic analy-sis of Plutonium 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 t

36、he time between sample purificationand isotopic analysis is 20 days. Operators are responsible fordetermining a maximum interval between purification andmass spectrometric analysis, based on an evaluation of241Amin-growth from decaying241Pu and required accuracy andprecision. Other atomic and molecu

37、lar species may interferewith total evaporation analyses, particularly if they cause achange in the ionization efficiency of the analyte during ananalysis. Carbon may disturb total evaporation measurements.It is recommended that operators perform validation tests onunique or complex samples by mixin

38、g known pure standardswith other constituents to create a matrix-matched standard.6.2 Care must be taken to avoid 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

39、 size, plannedhandling and processing of the sample, and knowledge of thelevels of contamination present in the 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

40、 spectrom-eter and trace uranium in chemicals or the filaments may biasmeasurement data.6.3 The total evaporation 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

41、presence of239Pu.Biases in the minor isotope data occur due to peak tailing fromthe major isotopes. The amount of 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 b

42、y measuring the abundancesensitivity under identical experimental conditions. A biascorrection may then be applied 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 measu

43、rement of minor isotopes.The use of an energy filter, ultra high-purity filaments andchemicals, effective sample purification, and low ionizationand evaporation temperatures to minimize238U interferencescan allow for the accurate measurement of small238Pu abun-dances by this technique. Another commo

44、nly used methodfor238Pu measurement when in low abundances is the alpha-spectrometry technique, following Test Method C 1415 orPractice D 3084.7. Apparatus7.1 Mass SpectrometerThe suitability of mass spectrom-eters for use with this method of analysis shall be evaluated bymeans of performance tests

45、described in this method and inPractice E 137. The mass spectrometer used should possess thefollowing characteristics: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 theproc

46、edure.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+. Resolution greaterthan 360 (full width at 1 % of peak height) and an abundancesensitivity of less than 10-5. For measuring minor isotop

47、es, anabundance sensitivity as low as achievable is recommended.7.1.3 An instrument capable of monitoring ion beam 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 filamen

48、tcurrent.7.1.4 A mechanism for changing samples.7.1.5 Multiple direct-current detectors (Faraday cups) or acombination 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 A pumping system to attain

49、a vacuum of less than 400Pa (3 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 3 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 instrument operation and tocollect and process data produced by the instrument.7.2 An optical pyrometer is recommended for determiningfilament temperatures.7.3 Filament preheating/degassing uni