ASTM E3063-2016 Test Method for Antimony Content Using Neutron Activation Analysis (NAA)《中子活化分析法(NAA)测定锑含量的试验方法》.pdf

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1、Designation: E3063 16Test Method forAntimony Content Using Neutron Activation Analysis (NAA)1This standard is issued under the fixed designation E3063; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu

2、mber 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 measurement of antimonyconcentration in plastics or other hydrocarbon or organicmatrix by using neutron activ

3、ation analysis (NAA). Thesample is activated by irradiation with neutrons from a researchreactor and the subsequently emitted gamma-rays are detectedwith a germanium semiconductor detector. The same systemmay be used to determine antimony concentrations rangingfrom 1 ng/g to 10 000 g/g with the lowe

4、r end of the rangelimited by numerous interferences and the upper limit estab-lished by the demonstrated practical application of NAA.1.2 This test method may be used on either solid or liquidsamples, provided that they can be made to conform in size andshape during irradiation and counting to a sta

5、ndard sample ofknown antimony content using very simple sample prepara-tion. Several variants of this method have been described in thetechnical literature.Amonograph is available which provides acomprehensive description of the principles of neutron activa-tion analysis using reactor neutrons (1).2

6、1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 appr

7、o-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tions are given in Section 9.2. Referenced Documents2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetry2.2 U.S. Government Document:4Code of

8、Federal Regulations, Title 10, Part 202.3 Joint Committee for Guides in Metrology (JCGM)Reports:5JCGM 100:2008, GUM 1995 , with minor corrections,Evaluation of measurement dataGuide to the expressionof uncertainty in measurement3. Terminology3.1 Definitions: See also Terminology E170.3.1.1 comparato

9、r standarda a reference standard ofknown antimony content whose specific activation and count-ing sensitivity (counts (mg of antimony)1) may be used toquantify the antimony content of a sample irradiated andcounted under the same conditions. Often, a comparatorstandard is selected to have a matrix c

10、omposition, physicalsize, density and shape very similar to the correspondingparameters of the sample to be analyzed. Differences in size,density, shape and matrix composition between sample andstandard may be corrected for using physical or empiricalmodels.3.1.2 gamma-ray spectrometera system compr

11、ising a de-tector which detects individual gamma-rays and converts theirenergy into an electronic pulse whose voltage is proportional tothe energy deposited in the detector, and a multichannelpulse-height analyzer which measures the pulse heights, as-signs a digital value and stores the individual c

12、ounts in thechannels of a gamma-ray spectrum according to the digitalvalues assigned.3.1.3 intensitythe probability of emission of a gamma-rayof a given energy per decay. Another commonly used term isgamma abundance.3.1.4 monitorany type of detector or comparison refer-ence material that can be used

13、 to produce a response propor-tional to the neutron fluence rate in the irradiation position, orto the radionuclide decay events recorded by the sampledetector.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of S

14、ubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved Oct. 1, 2016. Published October 2016. DOI: 10.1520/E3063-16.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, or

15、contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from the Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.5Document produced by Working G

16、roups of the Joint Committee for Guides inMetrology (JCGM). Available free of charge at BIPM website (http:/www.bipm.org).Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.4.1 DiscussionAn aluminum wire with 1 mg/g Aucontent is ofte

17、n used as a fluence rate monitor. Iron wires areused as well. It is important to distinguish that the monitor isnot a standard used to scale the antimony content of thesamples to be measured, but rather is used to normalize theanalysis system among samples irradiated simultaneously atdifferent posit

18、ions in the polyethylene irradiation sample con-tainer or among successive analytical passes within the proce-dure. When using reactors with highly reproducible fluencerate, such as those with 1% variation over long periods of time,monitors may not be necessary for every irradiation.3.1.5 neutron fl

19、uence ratethe fluence rate (see definitionin Terminology E170) of neutrons. In this test method it refersto the value at the site in the reactor where sample andcomparator standard are irradiated.3.1.6 pneumatic transfer systema system used to trans-port the sample to the irradiation site in the rea

20、ctor and then toa sample receiver.3.1.6.1 DiscussionIt may also be used to transport thesample directly to the counting station where the activity of thesample is measured. For the measurement of antimony, wherea long decay time between irradiation and counting is usuallyrequired, the samples are ma

21、nually transferred from the re-ceiver to the germanium semiconductor detector or to amechanical sample changer which transports them one by oneat the appropriate time to the counting position at the detector.3.1.7 research nuclear reactor, na nuclear reactor thatuses the fission of uranium to operat

22、e at a well-controlledpower level and produces neutrons that can be used forexperiments and for neutron activation analysis. Examples ofreactor types believed to be applicable to this test method areTRIGA, SLOWPOKE and MNSR; their operational character-istics are given in Refs (2-6).3.1.7.1 Discussi

23、onAnother term in common usage is re-search reactor. Reactor conditions which may make the reactorunsuitable for this test method (for example, very low neutronfluence rates or high operating temperature) are sample andreactor dependent. Such conditions should be considered priorto use of this test

24、method.3.1.8 standard uncertaintymeasurement uncertainty of theresults of a measurement expressed as a standard deviation(GUM, see 2.3).4. Summary of Test Method4.1 The test method can be applied directly to solid samplessuch as plastic pellets or cylindrical pieces of cable insulation.The weighed s

25、ample to be analyzed is placed in a polyethylenecontainer for transfer from the sample-loading port to theirradiation site in the reactor. Several samples, standards andmonitors may be irradiated simultaneously provided that theself-shielding effects of multiple samples on each other arewell underst

26、ood (7). After irradiation for a pre-selected time,the samples are returned to the sample receiver. After anappropriate decay period to allow the decay of short-livedradio-isotopes, typically 24 h, the samples are manuallyunpacked and transferred from the receiver to the germaniumsemiconductor detec

27、tor or to a mechanical sample changerwhich transports them one by one at the appropriate time to thecounting position at the detector. The signals from the detectorare sent to a multichannel pulse-height analyzer which mea-sures the energies of the individual gamma-rays and placesthem in a gamma-ray

28、 spectrum. The spectrum has peaks at thecharacteristic energies of the elements present in the sample.The spectrum for each sample is stored for subsequent analy-sis.4.2 The amount of total antimony (all chemical forms) inthe sample is proportional to the corrected and normalized peakarea and is qua

29、ntified by use of the corrected and normalizedpeak area of the comparator standard(s).4.3 When antimony is irradiated with neutrons, the atoms ofthe isotope121Sb capture neutrons and are converted to122Sbwhich is radioactive with a half-life of 2.72 days.122Sb decaysby emitting a beta-ray and gamma-

30、rays of several possibleenergies. From Ref (8), the main gamma-ray, at 564.2 keV, isemitted in 70.67 % of decays. The amount of total antimony(all chemical forms) in the sample is proportional to thecorrected number of counts in the peak at 564.2 keV. The areaof the peak at 564.2 keV is corrected fo

31、r counts beneath thepeak due to Compton scattered gamma-rays and for pulselosses (dead-time) in the combined detector-multichannelpulse-height analyzer system. All modern multichannel pulse-height analyzers accurately correct for pulse losses up to theirmaximum useable count-rates.4.3.1 The detector

32、 must have good energy resolution be-cause the peak at 564.2 keV must be well separated fromnearby peaks such as those from82Br at 554.3 keV and76As at559.1 keV.4.4 In addition to121Sb capturing neutrons to produce122Sb, the123Sb isotope captures neutrons to produce124Sb,with a 60-day half-life. Thi

33、s isotope has strong gamma lines at603 keV and 1691 keV. Measurement of both122Sb and124Sbprovides an additional verification of the methods accuracy.This standard employs the most sensitive122Sb gamma-ray, butthe same methods and equations apply equally to all gamma-rays of both isotopes.5. Signifi

34、cance and Use5.1 High levels of antimony are commonly used in flameretardant formulations for various materials. NAA is a testmethod that can be useful for verifying these levels and, forother materials, NAA can also be useful in establishing theamount of low level contamination, if any, with high s

35、ensitivityand high precision.5.2 Neutron activation analysis provides a rapid, highlysensitive, nondestructive procedure for antimony determina-tion in a wide range of matrices. This test method is indepen-dent of the chemical form of the antimony.5.3 This test method can be used for quality and pro

36、cesscontrol in the petrochemical and other manufacturingindustries, and for research purposes in a broad spectrum ofapplications.E3063 1626. Detection Limit and Range of Application6.1 Using a research nuclear reactor and germaniumsemiconductor detector, the estimated detection limit for anti-mony i

37、n plastics is 1 ng/g (9). This detection limit may bereduced by using a larger sample, a reactor with higher neutronfluence rates, higher counting efficiency detectors and longerirradiation and counting times. However, under the conditionsof this test method, the main factor determining the detectio

38、nlimit is the amount of interfering elements in the sample.6.1.1 The detection limit of 1 ng/g provided in this testmethod presumes clean materials. In materials containing highamounts of interfering elements, the detection limit may behigher. This detection limit of 1 ng/g implies that, for samples

39、actually containing 1 ng/g (not known by the analyst), there isa 50 % chance that the analysis will result in a peak areacorresponding to greater than 1 ng/g and it will be judged thatantimony was detected and a quantitative result will be given.6.1.2 For this same sample, there is also a 50 % chanc

40、e thatthe analysis will result in a peak area corresponding to less than1 ng/g and it will be judged that antimony was not detected anda result of “not detected” will be given. For samples containingno antimony (or less than 0.1 ng/g) there is a 2.5 % probabilitythat the result of the analysis will

41、be greater than 1 ng/g and aquantitative result will be given (false positive).6.2 Near the detection limit, the uncertainty in the measuredantimony mass fraction is 0.5 ng/g. This standard uncertainty iscaused mainly by statistical fluctuations in the Comptonbackground under the small antimony peak

42、 at 564.2 keV.6.3 With a detection limit of 1 ng/g, the limit of quantitation(for 10 % uncertainty) is 5 ng/g. This means that, for samplescontaining 5 ng/g antimony or more, it is possible to producean analysis result with 10 % standard uncertainty or less.6.4 At levels above 10 mg/g (1 %), non-lin

43、ear effects in therelation between observed peak area and antimony concentra-tion shall be considered and the application of corrections forsaturation effects such as neutron self-shielding shall be per-mitted.6.4.1 For samples with high antimony content, neutronself-shielding correction may use a p

44、rocedure such as that ofRef (10) which takes into account sample size, observedantimony content and the ratio of thermal to epithermal fluencerates of the reactor irradiation site used.7. Interferences and Necessary Corrections7.1 All radionuclides which emit high energy gamma-raysmay potentially in

45、terfere with the detection of the 564.2 keVgamma-ray of122Sb. When these gamma-rays are detected inlarge numbers, the high count-rate may saturate the detectorand force the analyst to count the sample farther from thedetector or to wait until the amount of radioactivity decreases.This reduces the se

46、nsitivity for the detection of antimony.Also,high energy gamma-rays which scatter in the detector by theCompton process and deposit only part of their energy in thedetector may produce counts in the gamma-ray spectrum near564.2 keV. These counts under the122Sb 564.2 keV gamma-raypeak make it more di

47、fficult to determine the peak area andincrease the uncertainty of the peak area due to countingstatistics.7.2 A specific potentially interfering radionuclide is76Aswhich emits a weak gamma-ray at 563.2 keV, almost the sameenergy as the gamma-ray of122Sb. However, this interferenceonly becomes signif

48、icant when there is as much arsenic asantimony in the sample and it can easily be corrected. Knowingthat the ratio of the areas of the76As peaks at 563.2 keV and559.3 keV is a constant for a given germanium detector and agiven counting geometry, approximately 0.025, one can correctthe interference f

49、or each sample using the observed area of the76As peak at 559.3 keV.7.3 There are a number of other potentially interferingradionuclides which emit gamma-rays near the122Sb energy of564.2 keV. They are listed in Table 1. In most cases theelements producing these nuclides will be present in the samplein low quantities and the interfering gamma-rays will have anegligible effect on the 564.2 keV peak area.7.3.1 However, for materials with expected low antimonycontent and which may contain these interfering elements inhigher quantities, it is prudent to verify the spectru