ASTM C1030-2010 Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry《用γ射线光谱法测定钚同位素成分的标准试验方法》.pdf

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1、Designation: C1030 10Standard Test Method forDetermination of Plutonium Isotopic Composition byGamma-Ray Spectrometry1This standard is issued under the fixed designation C1030; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye

2、ar 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 is applicable to the determination ofisotopic abundances in isotopically homogeneous plutonium-

3、bearing materials. This test method may be applicable to otherplutonium-bearing materials, some of which may requiremodifications to the described test method.1.2 The procedure is applicable to items containing pluto-nium masses ranging from a few tens of milligrams up to themaximum plutonium mass a

4、llowed by criticality limits.1.3 Measurable gamma ray emissions from plutonium coverthe energy range from approximately 30 keV to above 800 keV.K-X-ray emissions from plutonium and its daughters are foundin the region around 100 keV. This test method has beenapplied to all portions of this broad spe

5、ctrum of emissions.1.4 The isotopic abundance of the242Pu isotope is notdirectly determined because it has no useful gamma-raysignature. Isotopic correlation techniques may be used toestimate its relative abundance Refs (1) and (2).21.5 This test method has been demonstrated in routine usefor isotop

6、ic abundances ranging from 99 to 50 %239Pu. Thistest method has also been employed for isotopic abundancesoutside this range.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all o

7、f thesafety concerns, if any, associated with 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:3C697 Test Methods for C

8、hemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade PlutoniumDioxide Powders and PelletsC698 Test Methods for Chemical, Mass Spectrometric, andSpectrochemicalAnalysis of Nuclear-Grade Mixed Oxides(U, Pu)O2)C982 Guide for Selecting Components for Energy-Dispersive X-Ray Fluoresc

9、ence (XRF) Systems4C1207 Test Method for Nondestructive Assay of Plutoniumin Scrap and Waste by Passive Neutron CoincidenceCountingC1316 Test Method for Nondestructive Assay of NuclearMaterial in Scrap and Waste by Passive-Active NeutronCounting Using252Cf ShufflerC1458 Test Method for Nondestructiv

10、eAssay of Plutonium,Tritium and241Am by Calorimetric AssayC1493 Test Method for Non-Destructive Assay of NuclearMaterial in Waste by Passive andActive Neutron CountingUsing a Differential Die-Away SystemC1500 Test Method for Nondestructive Assay of Plutoniumby Passive Neutron Multiplicity CountingE1

11、81 Test Methods for Detector Calibration andAnalysis ofRadionuclidesE267 Test Method for Uranium and Plutonium Concentra-tions and Isotopic Abundances2.2 ANSI Standards:5ANSI/IEEE Std 325-1996 IEEE Standard Test Proceduresfor Germanium Gamma-Ray Detectors1This test method is under the jurisdiction o

12、f ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10 on NonDestructive Assay.Current edition approved June 15, 2010. Published July 2010. Originallyapproved in 1984. Last previous edition approved in 2003 as C1030 03. DOI:10.1520/C1030-10.2The boldface nu

13、mbers in parentheses refer to the list of references at the end ofthis standard.3For 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 Summary page

14、onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Bo

15、x C700, West Conshohocken, PA 19428-2959, United States.ANSI N15.36 Measurement Control Program Nonde-structive Assay Measurement Control and Assurance3. Summary of Test Method3.1 The intensities of gamma-rays emitted from aplutonium-bearing item are determined from a gamma-rayspectrum obtained with

16、 a High-Purity Germanium (HPGe)detector. The method has also been used with CdTe detectors.3.2 The atom ratio, Ni/Nk, for isotopes i and k is related tothe photopeak counting intensity, C(Eji), for gamma ray j withenergy Ejemitted from isotope i by:NiNk5C Eji!C Elk!T1/2iT1/2kBRlkBRjiREEl!REEj!(1)whe

17、re:RE(Ei) = relative detection efficiency for a gamma-ray ofenergy Ei,T1/2i= half-life of isotope i, andBRji= gamma-ray branching ratio or branching intensity(usually expressed as gamma-rays per disintegra-tion) of gamma ray j from isotope i.3.3 The half lives T1/2and the branching ratios BR areknow

18、n, published nuclear data. The photopeak counting inten-sity C(E) is determined from the gamma ray spectrum of themeasured item.3.4 The relative detection efficiency, RE(E), is a function ofgamma-ray energy and arises from the combined effects ofdetector response, attenuation due to absorbers and co

19、ntainerwalls, and self-absorption within the measured item forgamma-rays of differing energies. The relative detection effi-ciencies are determined for each measured item from theobserved gamma spectrum by considering a series of gammarays from a single isotope. The quotient of the photopeakcounting

20、 intensity for gamma ray j with energy Ejemitted fromisotope i and the branching ratio of gamma ray j from isotopei is proportional to the relative detection efficiency at energy Ej.This quotient defines the shape of the relative efficiency as afunction of energy.CEji!BRjiaSNiT1/2i D REEj! (2)3.5 Al

21、l factors in Eq 1 are either determined from thegamma ray spectrum of the measured item or are known,published nuclear constants. The absolute atom ratios aredetermined without recourse to standards or calibration by thisso-called Intrinsic Calibration technique.4. Significance and Use4.1 The determ

22、ination of plutonium isotopic composition bygamma-ray spectrometry is a nondestructive technique andwhen used with other nondestructive techniques, such ascalorimetry (Test Method C1458) or neutron counting (TestMethods C1207, C1316, C1493, and C1500), can provide awholly nondestructive plutonium as

23、say necessary for materialaccountancy and safeguards needs.4.2 Because gamma-ray spectrometry systems are typicallyautomated, the routine use of the test method is fast, reliable,and is not labor intensive. The test method is nondestructive,requires no sample preparation, and does not create wastedi

24、sposal problems.4.3 This test method assumes that all plutonium in themeasured item has the same isotopic distribution, often calledisotopic homogeneity (see 7.2.4 and 7.2.5).4.4 The242Pu abundance is not measured by this testmethod and must be estimated from isotopic correlationtechniques, stream a

25、verages, historical information, or othermeasurement techniques.4.5 Americium-241 is a daughter product of241Pu.The241Am/239Pu atom ratio can also be determined by meansof this test method (assuming a homogeneous isotopic distri-bution of plutonium and241Am). The determination ofthe241Am/239Pu atom

26、ratio is necessary for the correct inter-pretation of a calorimetric heat measurement.4.6 The isotopic composition of a given batch or item ofplutonium is an attribute of that item and, once determined, canbe used in subsequent inventory measurements to verify theidentity of an item within the measu

27、rement uncertainties.4.7 The method can also measure the ratio of other gamma-emitting isotopes to plutonium assuming they have the samespatial distribution as the plutonium in the item. Some of these“other” gamma-emitting isotopes include isotopes of uranium,neptunium, curium, cesium, and other fis

28、sion products. Thesame methods of this standard can be used to measure theisotopic composition of uranium in items containing onlyuranium (3, 4, 5, 6).5. Interferences5.1 Because of the finite resolution of even the best qualityHPGe detectors, the presence of other gamma-emitting sourcesmust be asse

29、ssed for their effects on the isotopic abundancedetermination.5.1.1 The detector used for the spectral measurements shallbe adequately shielded from other nearby plutonium sources.Background spectra shall be collected to ensure the effective-ness of detector shielding and to identify the backgroundr

30、adiations.5.1.2 If fission products are present in the item beingmeasured, they will contribute additional gamma-ray spectralpeaks. These peaks occur mainly in the 500 to 800-keV energyrange and may affect the intensity determination of plutoniumand americium peaks in this region. These high-energyg

31、amma-rays from fission products also produce contributionsto the Compton background below 500 keV that decrease theprecision for peak intensity determination in this region.5.1.3 For mixed plutonium-uranium oxide-bearing items,the appropriate corrections for the spectral peaks produced byuranium gam

32、ma emission shall be applied. The main interfer-ences from uranium are listed in Table 1.5.1.4 Other interference-producing nuclides can be rou-tinely present in plutonium-bearing materials. The gamma raysfrom these nuclides must be assessed for their interferenceeffects on the multiplets used for t

33、he plutonium isotopicanalysis and the proper spectral corrections applied. Some ofthese interfering nuclides include:237Np and itsdaughter233Pa,243Am and its daughter239Np,233U, and the Thdecay chain daughters of232U and236Pu.C1030 1025.2 Count-rate and coincident-summing effects may alsoaffect the

34、isotopic abundance determination. This is especiallyimportant for items having high241Am concentrations. Ran-dom summing of the intense 59.5-keV241Am gamma ray withother intense gamma radiations produces spurious spectralpeaks (7) that can interfere with the isotopic analysis. Thin(typically 0.5 to

35、2 mm) cadmium or tin (which is less toxic)absorbers should be placed on the front face of the detector tokeep the height of the 59.5 keV gamma-ray peak equal to orless than the height of the most intense peaks in the 100-keVregion.6. Apparatus6.1 Cooled High-Purity Germanium Detector,PreamplifierCoo

36、ling of the HPGe crystal may come fromliquid nitrogen (LN2) or from electric or electro-mechanicalcoolers that do not use LN2. The configuration of the HPGedetector may be planar, semi-planar, or coaxial with the type,size and energy resolution of the detector chosen to accommo-date the energy range

37、 of analysis for the desired measurements.Planar or semi-planar detectors with energy resolution (full-width at half maximum) at 122 keV better than 650 eV are bestfor analysis of spectra in the 60 to 450 keV region. Largervolume coaxial detectors with efficiencies (relative to a 3 3 3NaI(Tl) at 133

38、2 keV for a point source at a distance of 10 cm(ANSI/IEEE Std 325-1996) of 25 to 100 % are used foranalysis in the energy regions above 120 keV. Resolution of 2keV or better at 1332 keV is preferred.6.2 High Voltage Supply, Linear Amplifier, Analog-to-Digital Converter (ADC), Multichannel Pulse-Heig

39、ht Analyzer(MCA)Systems containing these components compliant withGuide C982 may be used. A preferred and more convenientchoice is an integrated digital spectroscopy system containingall components in a single unit with a high speed computerinterface. Analysis of spectra in the 100 keV-region requir

40、es atleast 4096 channels of data. Analysis in higher energy regionsrequires a minimum of 8192 channels of data with 16 384 datachannels becoming more widely used.6.3 High count rate applications require the use of pile-uprejection circuitry. Digital stabilization may be desirable forlong count times

41、 under conditions of poor environmentalcontrol to ensure the quality of the spectral data. High qualitydigital spectroscopy systems fulfill all of these requirementsand have been shown to have minimal degradation on pluto-nium isotopic composition measurement results at input count-ing rates as high

42、 as 100 kHz (8).6.4 Because of the complexity of plutonium spectra, datareduction is usually performed by computer. Computerizedanalysis methods are well developed and have been highlyautomated with the development of various analysis softwarecodes (8, 9, 10, 11, 12, 13, 14). Analysis software is co

43、mmer-cially available as are all of the required data acquisitioncomponents.7. Precautions7.1 Safety PrecautionsPlutonium-bearing materials areboth radioactive and toxic. Use adequate laboratory facilitiesand safe operating procedures in handling items containingthese materials. Follow all safe oper

44、ating procedures andprotocols specific to the facility or location where the measure-ments are being made.7.2 Technical Precautions:7.2.1 Preclude or rectify counting conditions that mayproduce spectral distortions. Use pulse pile-up rejection tech-niques if high count rates are encountered. Use abs

45、orbers whenappropriate to reduce the intensity of the 59.5 keV gamma-rayof americium (see 5.2). Temperature and humidity fluctuationsin the measurement environment may cause gain and zero-level shifts in the gamma-ray spectrum. Employ environmentalcontrols or digital stabilization, or both, in this

46、case. Failure toisolate the electronic components from other electrical equip-ment or the presence of noise in the AC power may alsoproduce spectral distortions.7.2.2 The decay of241Pu is shown in Fig. 1. The alphadecay branch proceeds through the daughter237U whichdecays with a 6.75 day half-life t

47、o237Np. It takes 67 days toreach 99.9 % of secular equilibrium for this branch of thedecay. After secular equilibrium has been attained the stronggamma rays at 164.6, 208.0, 267.5, 332.4, 335.4, 368.6, and370.9 keV from the decay of237U may be used to directlydetermine241Pu. These major gamma rays f

48、rom the decayof237U also have an identical energy component from the betadecay branch of241Pu proceeding through241Am. The241Amcomponent of these “co-energetic” peaks must be accountedfor in the analysis. If secular equilibrium has not been reached,gamma rays (usually the 148.57-keV peak) from the d

49、irectdecay of241Pu to237U must be used to determine the241Puisotopic fraction. At all times the gamma rays from the decayof237U may be used to determine the relative efficiency.7.2.3 The facility may place high-Z absorbers within thesealed, plutonium-bearing container to reduce external radia-tion exposure to the handler. As little as116 in. (0.16 cm) oflead surrounding the plutonium will absorb the majority of theuseful gamma rays in the 100 to 200-keV region and mayinvalidate the measurement, depending upon the energy rangeof the analysis.7.2.4 The isotopic comp