1、Designation: C 1030 03Standard Test Method forDetermination of Plutonium Isotopic Composition byGamma-Ray Spectrometry1This standard is issued under the fixed designation C 1030; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、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 test method is applicable to the determination ofisotopic abundances in isotopically homogeneous Pu-bear
3、ingmaterials. 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 sample sizes rangingfrom a few tenths of a gram up to the maximum sample weightallowed by criticality limits.1.
4、3 Because242Pu has no useful gamma-ray signature, itsisotopic abundance is not determined. Isotopic correlationtechniques may be used to estimate its relative abundance(Refs 1, 2).21.4 This test method has been demonstrated in routine usefor isotopic abundances ranging from 96 to 55 %239Pu. Thistest
5、 method has also been employed for isotopic abundancesoutside this range.1.5 The values stated in SI units are to be regarded as thestandard.1.6 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
6、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:C 697 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade PlutoniumDioxide Powders and Pelle
7、ts3C 698 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade Mixed Oxides(U, Pu)O2)3C 982 Guide for Selecting Components for Energy-Dispersive X-Ray Fluorescence (XRF) Systems3C 1207 Test Method for Nondestructive Assay of Plutoniumin Scrap and Waste by Passiv
8、e Neutron CoincidenceCounting3C 1458 Test Method for Nondestructive Assay of Pluto-nium, Tritium and241Am by Calorimetric Assay3C 1493 Test Method for Non-Destructive Assay of NuclearMaterial in Wast by Passive and Active Neutron CountingUsing a Differential Die-Away System3C 1500 GTest Method for N
9、ondestructive Assay of Pluto-nium by Passive Neutron Multiplicity Counting3E 181 General Methods for Detector Calibration and Analy-sis of Radionuclides4E 267 Test Method for Uranium and Plutonium Concentra-tions and Isotopic Abundances42.2 ANSI Standards:ANSI N15.35 Guide to Preparing Calibration M
10、aterial forNondestructive Assay Systems that Count Passive GammaRays53. Summary of Test Method3.1 Relative intensities of gamma-rays from a plutoniumsample are determined from a gamma-ray spectrum obtainedwith a high-resolution Ge detector.3.2 The atom ratio, Ni/Nj, for isotopes i and j is related t
11、o therelative counting intensities, Iiand Ij, for the gamma-rays ofenergy Eiand Ejby:NiNj5 CijIieiejIj(1)Cij5T1/2iT1/2jBjBi(2)where:e = relative detection efficiency for a gamma-ray atenergy E,1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct re
12、sponsibility of Subcommittee C26.10 on Nondestruc-tive Assay.Current edition approved July 10, 2003. Published August 2003. Originallyapproved in 1984. Last previous edition approved in 2001 as C 1030 95(2001).2The boldface numbers in parentheses refer to the list of references at the end ofthis sta
13、ndard.3Annual Book of ASTM Standards, Vol 12.01.4Annual Book of ASTM Standards, Vol 12.02.5Available from the American National Standards Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
14、ed States.T1/2= half-life, andB = gamma-ray branching intensity (usually expressedas the gamma-ray emission probability per disinte-gration).3.3 The conversion factors, Cij, are computed from knownhalf-lives and gamma-ray branching intensities.3.4 The relative detection efficiency, e, is a function
15、ofgamma-ray energy and results from the combined effects ofdetector response, attenuation due to absorbers and containerwalls, and self-absorption within the sample for gamma-rays ofdiffering energies. The relative detection efficiencies are deter-mined for each sample from the observed gamma spectr
16、um.4. Significance and Use4.1 The determination of isotopic composition by gamma-ray spectrometry is a nondestructive technique and when usedwith other nondestructive techniques, such as calorimetry (TestMethod C 1458) or neutron counting (Test MethodsC 1207C 1493C 1500), can provide a totally nonde
17、structiveplutonium assay necessary for material accountancy and safe-guards needs.4.2 Since gamma-ray spectrometry systems are typicallyautomated, the routine use of the test method is fast, reliable,and is not labor intensive. Since the test method is nondestruc-tive, requiring no sample preparatio
18、n, it does not create wastedisposal problems.4.3 This test method assumes that the isotopic compositionof plutonium in the sample being measured is homogeneous(see see 7.2.4 and (5).4.4 The242Pu abundance is not measured by this test methodand must be estimated from isotopic correlation techniques,s
19、tream averages, historical information, or other measurementtechniques.4.5 A daughter product of241Pu is241Am. The241Am/239Puatom ratio can also be determined by means of this test method(assuming a homogeneous isotopic distribution of plutoniumand241Am) and is necessary for the correct interpretati
20、on of acalorimetric heat measurement.4.6 The isotopic composition of a given batch or sample ofplutonium is an attribute of that sample and, once determined,can be used in subsequent inventory measurements to verifythe identity of a sample within the measurement uncertainties.4.7 The method can also
21、 measure the ratio of other gammaemiting isotopes to plutonium assuming they have the samespatial distribution as the plutonium in the sample. Some ofthese “other” gamma-emitting isotopes include isotopes ofuranium, neptium, curium, cesium, and other fission products.(The same methods of this standa
22、rd can be used to measure theisotopic composition of uranium in samples containing onlyuranium (46).5. Interferences5.1 Due to the finite resolution of even the best quality ofgermanium detectors, the presence of other gamma-emittingsources must be assessed for their effects on the isotopicabundance
23、 determination.5.1.1 The germanium detector used for the spectral mea-surements shall be adequately shielded from other nearbyplutonium sources. Background spectra shall be collected toensure the effectiveness of detector shielding and to identifythe background radiations.5.1.2 If fission products a
24、re present in the sample 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-energygamma-rays from fission products als
25、o 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 samples, theappropriate corrections for the spectral peaks produced byuranium gamma emission shall be applied. The main in
26、terfer-ences due to 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 the plutonium isotopicanalysis and the p
27、roper spectral corrections applied. Some ofthese interfering nuclides would include:237Np and itsdaughter233Pa,239Np,243Am, and233U.5.2 Count-rate and coincident summing effects may alsoaffect the isotopic abundance determination. This is especiallyimportant for samples having high americium concent
28、rations(typically greater than241Pu ingrowth). Summing of the intense59.5-keV transition with other intense gamma radiations pro-duces spurious spectral peaks (7). Thin (typically 0.5 to 2 mm)cadmium or tin (which is less toxic) absorbers shall be placedon the front face of the detector to keep the
29、height of the 59.5keV gamma-ray peak equal to or less than the height of themost intense peaks in the 100-keV region.6. Apparatus6.1 Germanium Detector (with liquid nitrogen supply),Preamplifier and High-Voltage SupplyEnergy resolution ofthe detector for spectra collected below 400 keV should bebett
30、er than 600 eV full-width-at-half-maximum (FWHM) at122 keV. Purchase specifications of 550 eV or less shouldensure a working resolution of 600 eV or better. Thesedetectors are generally intrinsic, planar Ge of a few cubiccentimeters active volume. For the energy regions above 400keV, a large volume
31、Ge detector with an active volume of 40cm3or greater and with resolution of 2.0 keV or better at 1332keV is preferred.6.2 Linear Amplifier, Analog-to-Digital Converter (ADC),Multichannel Pulse-Height Analyzer (MCA)The ADC-MCAcombination shall be capable of at least 4K channel conversionTABLE 1 Gamma
32、-Ray Interferences Due to Uranium in (Pu, U)O2MaterialsEnergy(keV)BranchingIntensity(%g/disinte-gration)Isotope143.77 10.7235U163.36 4.85235U185.72 56.1235U202.12 1.07235U205.31 4.87235UC1030032and storage. More detailed descriptions of these componentscan be found in Guide C 982.6.3 High count rate
33、 applications require the use of pile-uprejection circuitry. Digital stabilization may be desirable forlong count times or poor environmental control to ensure thequality of the spectral data.6.4 Because of the complexity of plutonium spectra, datareduction is usually performed by computer. Several
34、softwarecodes are available that perform the spectral analysis andisotopic abundance calculations on a computer (Refs 811).6.5 All of the above apparatus is commercially available.Electronic modules are either NIM standard, NIM compatible,or self-contained, fully integrated digital signal processing
35、units. Many gamma-ray spectrometry systems are interfaced toa computer. This permits the isotopic abundance determinationprocedure to be automated.7. Precautions7.1 Safety PrecautionsPlutonium-bearing materials areboth radioactive and toxic. Use adequate laboratory facilitiesand safe operating proce
36、dures in handling samples containingthese materials. Safe handling practices are outlined in Refer-ences (12-14).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.
37、Use absorbers 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, i
38、n this 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 alpha decay branch of241Pu proceeds through thedaughter237U, which in turn decays to237Np with a half-life of6.75 days. Ab
39、out eight weeks are required for secular equilib-rium to be achieved. If less than eight weeks have elapsed sinceseparation, use gamma rays produced by the parent,241Pu, forisotopic abundance determinations; for example, the 148.57keV peak. However, gamma rays arising from decay of thedaughter,237U,
40、 can be used for relative efficiency calculations.7.2.3 Preferably, do not include high-Z absorbers in samplepackaging. As little as18 in. (0.32 cm) of lead surrounding theplutonium will absorb the majority of the useful gamma rays inthe 100 to 200-keV region and may invalidate the measure-ment.7.2.
41、4 The isotopic composition of all the plutonium in thesample must be the same. The technique does not apply tononuniform mixtures of different isotopic composition. How-ever, the physical distribution of the plutonium within thesample may be nonuniform with no adverse effect on theresults.7.2.5 The2
42、41Am/239Pu atom ratio must be uniform in all theplutonium in the sample, in order to obtain reliable specificpower measurements to use in interpreting calorimetry results.Certain types of Pu materials with nonhomogeneous Am-Pudistributions (salt residues) have been shown to be amenable toassay by th
43、is test method with slight modifications (15, 16).These materials have a low density salt matrix containing mostof the americium while most of the plutonium is dispersedthroughout this matrix as high density localizations or freemetal shot.7.2.6 Plutonium-bearing materials, especially plutoniumfluor
44、ide compounds, should not be stored in the vicinity of, oron, the germanium detectors. High energy neutrons emitted bythese materials can produce trapping centers in the germaniumcrystals and severely degrade the resolution of the detectors.The use on N-type detectors which are less susceptible tone
45、utron damage, can prolong useful detector life.8. Calibration, Standardization, and MeasurementControl8.1 ApparatusThe energy calibration of the spectrometrysystem can be adjusted using a gamma-emitting check sourceor a plutonium-bearing sample because the plutonium gamma-ray energies are well known
46、. A listing of the intense plutoniumradiations that are suitable for an energy calibration procedureis given in Table 2. See also Test Methods E 181 and Reference17.8.2 Reference Materials:8.2.1 The expression relating atom ratios to detected peakintensities contains only fundamental constants (see
47、Eq 1 andEq 2) and does not depend upon reference standards. Referencestandards can be used to identify biases in the values ofmeasured fundamental constants and as an aid in identifyingpossible spectral interferences.8.2.2 Working reference materials with isotopic composi-tion traceable to the Natio
48、nal Institute of Standards andTechnology (NIST) (or other certifying standards bodies)TABLE 2 Energies and Gamma-Ray Branching IntensitiesAofProminent Pu and Am Spectral PeaksEnergy(keV)Branching Intensity(g/disintegration, %)Isotope59.54 0.359241Am125.29 4.08 3 105 241Am129.29 6.26 3 105 239Pu148.5
49、7 1.87 3 106 241Pu152.68 9.37 3 106B 238Pu160.28 4.02 3 106 240Pu164.48C4.53 3 107 241Pu-237U6.67 3 107 241Am203.54 5.60 3 106 239Pu208.00C5.16 3 106B 241Pu-237U7.91 3 106 241Am335.44C2.39 3 108 241Pu-237U4.96 3 106 241Am345.01 5.59 3 106 239Pu368.61C1.05 3 108 241Pu-237U2.17 3 106 241Am375.04 1.57 3 105 239Pu413.71 1.49 3 105 239Pu642.48 1.245 3 107 240Pu645.97 1.49 3 107 239Pu662.42 3.64 3 106 241Am717.72 2.74 3 108 239Pu721.99 1.96 3 106 241AmABranching intensities from Ref 15, except where noted.BBranching intensity from “Handbook of Nuclear Data fo
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