1、Designation: C1133/C1133M 10Standard Test Method forNondestructive Assay of Special Nuclear Material in Low-Density Scrap and Waste by Segmented Passive Gamma-Ray Scanning1This standard is issued under the fixed designation C1133/C1133M; the number immediately following the designation indicates the
2、 yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the transmission-corrected
3、non-destructive assay (NDA) of gamma-ray emitting specialnuclear materials (SNMs), most commonly235U,239Pu,and241Am, in low-density scrap or waste, packaged in cylin-drical containers. The method can also be applied to NDA ofother gamma-emitting nuclides including fission products.High-resolution ga
4、mma-ray spectroscopy is used to detect andmeasure the nuclides of interest and to measure and correct forgamma-ray attenuation in a series of horizontal segments(collimated gamma detector views) of the container. Correc-tions are also made for counting losses occasioned by signalprocessing limitatio
5、ns (1-3).21.2 There are currently several systems in use or underdevelopment for determining the attenuation corrections forNDA of radioisotopic materials (4-8). A related technique,tomographic gamma-ray scanning (TGS), is not included inthis test method (9, 10, 11).1.2.1 This test method will cover
6、 two implementations ofthe Segmented Gamma Scanning (SGS) procedure: (1) IsotopeSpecific (Mass) Calibration, the original SGS procedure, usesstandards of known radionuclide masses to determine detectorresponse in a mass versus corrected count rate calibration thatapplies only to those specific radio
7、nuclides for which it iscalibrated, and (2) Efficiency Curve Calibration, an alternativemethod, typically uses non-SNM radionuclide sources todetermine system detection efficiency vs. gamma energy andthereby calibrate for all gamma-emitting radionuclides ofinterest (12).1.2.1.1 Efficiency Curve Cali
8、bration, over the energy rangefor which the efficiency is defined, has the advantage ofproviding calibration for many gamma-emitting nuclides forwhich half-life and gamma emission intensity data are avail-able.1.3 The assay technique may be applicable to loadings up toseveral hundred grams of nuclid
9、e in a 208-L 55-gal drum,with more restricted ranges to be applicable depending onspecific packaging and counting equipment considerations.1.4 Measured transmission values must be available for usein calculation of segment-specific attenuation corrections at theenergies of analysis.1.5 A related met
10、hod, SGS with calculated correction fac-tors based on item content and density, is not included in thisstandard.1.6 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem s
11、hall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.7 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 app
12、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 10.2. Referenced Documents2.1 ASTM Standards:3C1030 Test Method for Determination of Plutonium Isoto-pic Composition by Gamma-Ray Spe
13、ctrometryC1128 Guide for Preparation of Working Reference Mate-rials for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC1207 Test Method for Nondestructive Assay of Plutoniumin Scrap and
14、Waste by Passive Neutron CoincidenceCountingC1210 Guide for Establishing a Measurement System Qual-ity Control Program for Analytical Chemistry Laboratories1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10 o
15、n NonDestructive Assay.Current edition approved Jan. 1, 2010. Published February 2010. Originallyapproved in 1996. Last previous edition approved in 2003 as C1133 03. DOI:10.1520/C1133_C1133M-10.2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.3For r
16、eferenced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、West Conshohocken, PA 19428-2959, United States.Within the Nuclear IndustryC1215 Guide for Preparing and Interpreting Precision andBias Statements in Test Method Standards Used in theNuclear IndustryC1316 Test Method for Nondestructive Assay of NuclearMaterial in Scrap and Waste by Passive-Active Ne
18、utronCounting Using252Cf ShufflerC1458 Test Method for NondestructiveAssay of Plutonium,Tritium and241Am by Calorimetric AssayC1490 Guide for the Selection, Training and Qualificationof Nondestructive Assay (NDA) PersonnelC1592 Guide for Nondestructive Assay MeasurementsC1673 Terminology of C26.10 N
19、ondestructiveAssay Meth-odsE181 Test Methods for Detector Calibration andAnalysis ofRadionuclides2.2 ANSI Standards:4ANSI/IEEE 325 Test Procedures for Germanium Gamma-Ray DetectorsANSI N15.36 Measurement Control ProgramNondestructive Assay Measurement Control and Assur-ance3. Terminology3.1 Refer to
20、 Terminology C1673 for terminology defini-tions.4. Summary of Test Method4.1 The assay of the nuclides of interest is accomplished bymeasuring the intensity of one or more characteristic gammarays from each nuclide. Corrections are made for countrate-related losses and attenuation by the item. The a
21、ppropriatemass or efficiency calibration then provides the relationshipbetween observed gamma-ray intensity and nuclide content.4.2 Either of two distinct calibration methods can be used:4.2.1 Isotope Specific Calibration provides assay results foronly those radionuclides for which the SGS is specif
22、icallycalibrated. Calibration is performed using standards containingthe radionuclides to be assayed.4.2.2 Effciency Curve Calibration entails determination ofthe system detection efficiency as a function of gamma rayenergy. Analysis of assay data consists of using the energy ofa peak to infer the e
23、mitting radionuclide, and then calculatingthe radionuclide mass from the specific activity and the gammaemission intensity of the radionuclide, and the corrected countrate and detector efficiency at the peak energy.4.3 The assay item is rotated about its vertical axis andscanned segment by segment a
24、long that axis, thereby reducingthe effects of nonuniformity in both matrix density and nuclidedistribution (see Fig. 1).4.4 Count rate-dependent losses from pulse pile-up andanalyzer dead time are corrected for by electronic modules, aradioactive source, a pulser, or a combination of these.4.5 The
25、average linear attenuation coefficient of each hori-zontal segment is calculated by measurement of the transmittedintensity of an appropriate external gamma-ray source. Thesource is mounted directly opposite the gamma-ray detector, onthe far side of the assay item (see Fig. 1).4.6 Two conditions mus
26、t be met to optimize SGS assayresults as follows:4.6.1 The particles containing the nuclides of interest mustbe small enough to minimize self-absorption of emitted gammaradiation (13).4.6.1.1 Under specific conditions, particles large enough toprovide significant self absorption (lumps ) may be assa
27、yedaccurately. These conditions include use of specific nuclidedifferential peak calibration and calibration using mass stan-dards that have the same attenuation characteristics over theenergy range used for quantitative measurements as the mate-rials to be assayed.4.6.1.2 An alternative approach to
28、 mass calibration withstandards that contain the same sized particles is to applycorrection algorithms that are based on the differential responseof two or more peaks at different energies from the samenuclide. For example, the 129 and 414 keV peaks of239Pu orthe 144 and 186 keV peaks of235U could b
29、e used (see 7.7).4.6.1.3 The presence of lumps in material being assayedalso can be detected using differential peak response algo-rithms.4.6.2 The mixture of material within each item segmentmust be sufficiently uniform to apply an attenuation correctionfactor, generally computed from a measurement
30、 of gamma-raytransmission through the segment.4.7 The corrected gamma-ray count rates for the nuclides ofinterest are determined on a segment-by-segment basis. Theprecision of the measured count rate of each gamma ray usedfor analysis is also estimated on a segment-by-segment basis.At the completion
31、 of the measurement of all segments,corrected count rates are summed, and mass values for the4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.FIG. 1 Typical Arrangement for Segmented Gamma-Ray ScanningC1133/C1133M 102nucli
32、des of interest in the entire container are calculated basedeither on comparisons to appropriate calibration materials orfrom the gamma emission rates determined from the segmentefficiencies determined over the energy range of interest. Basedon counting statistics for individual segments, precision
33、valuesare propagated to obtain the estimated precision of the analysis.4.8 In the event that a single nuclide of an element ismeasured and the total element mass is required (forexample,239Pu and total plutonium), it is common practice toapply a known or estimated nuclide/total element ratio to then
34、uclide assay value to determine the total element content.4.8.1 Isotope ratios can be determined using gamma isoto-pic analysis techniques such as those described in Test MethodC1030.5. Significance and Use5.1 Segmented gamma-ray scanning provides a nondestruc-tive means of measuring the nuclide con
35、tent of scrap and wastewhere the specific nature of the matrix and the chemical formand relationship between the nuclide and matrix may beunknown.5.2 The procedure can serve as a diagnostic tool thatprovides a vertical profile of transmission and nuclide concen-tration within the item.5.3 Item prepa
36、ration is generally limited to good waste/scrap segregation practices that produce relatively homoge-neous items that are required for any successful waste/inventory management and assay scheme, regardless of themeasurement method used.Also, process knowledge should beused, when available, as part o
37、f a waste management programto complement information on item parameters, containerproperties, and the appropriateness of calibration factors.5.4 To obtain the lowest detection levels, a two-pass assayshould be used. The two-pass assay also reduces problemsrelated to potential interferences between
38、transmission peaksand assay peaks. For items with higher activities, a single-passassay may be used to increase throughput.6. Interferences6.1 Radionuclides may be present in the assay item thatproduce gamma rays with energies that are the same or verynearly the same as the gamma rays suggested for
39、nuclide ortransmission measurement. The areas of the closely spacedpeaks that are produced in the gamma-ray spectrum cannot becalculated by simple spectroscopic procedures. Peak fittingsoftware routines may be able to resolve closely spaced peaksin some cases; alternatively, the nuclide of interest
40、mayproduce other gamma rays that may be used for analysis.6.1.1 The peak produced by the 661.6-keV gamma ray from137Cs would interfere with calculation of the area of the241Am peak produced by its 662.4-keV gamma ray. The721.9-keV gamma ray of241Am may be a useful alternative.6.1.2 The peak produced
41、 by the 765.8-keV gamma ray from95Nb would interfere with calculation of the area of the238Pupeak produced by its 766.4-keV gamma ray. The 786.3-keVgamma ray of238Pu may be a useful alternative.6.1.3 Occasionally,237Np is found in the presence of pluto-nium. The237Np daughter,233Pa, emits a gamma ra
42、y at 415.8-keV along with several gamma rays in the range from 300 to400 keV. Peaks from these gamma rays would interfere withcalculation of the area of the239Pu peak produced by its413.7-keV gamma ray and several other often used peaksfrom239Pu. In this case, the peak produced by the 129.3-keVgamma
43、 ray of239Pu may be the only reasonable alternative.6.1.4 The peak produced by the 63.1-keV gamma rayfrom169Yb, sometimes used as the transmission sourcefor235U assays, may interfere with calculation of the area ofthe peak produced by the 59.5-keV gamma ray of241Am,which is used as the count rate co
44、rrection source. The169Ybgamma ray can be sufficiently attenuated by placing a cadmiumabsorber over the transmission source or the problem can beavoided altogether by using a two-pass assay. In a two-passassay, the first measurement pass measures the intensity of thetransmission source for each segm
45、ent. The second measure-ment pass measures the intensity of the 413.7-keV239Pugamma-ray emission from each segment with the transmissionsource shutter closed.6.1.5 Transmission source peaks may have errors intro-duced by the presence of a radionuclide in the assay materialthat emits gamma rays at or
46、 near one or more of the measuredtransmission energies. The affected measurements will then behigher than the actual transmissions through the item, leadingto calculation of a lower than actual correction factor andquantity of measured radionuclide.6.2 In the case of239Pu assays using75Se as a trans
47、missionsource, random coincident summing of the 136.00 and 279.53-keV gamma-ray emissions from75Se produces a low-intensitypeak at 415.5-keV that interferes with calculation of the area ofthe239Pu peak produced by its 413.7-keV gamma ray. Theeffects of this sum-peak can be reduced by attenuating the
48、radiation from the transmission source to the lowest intensityrequired for transmission measurements of acceptable preci-sion. This problem also can be avoided by making a two-passassay.6.3 Peaks may appear at the gamma-ray energies used foranalysis when there is no nuclide present on the turntable.
49、 Thelikely cause is excessive amounts of nuclide stored in thevicinity of the detector. The preferred solution to this problemis removal of the nuclide from the vicinity and restraint ofnuclide movements around the system during measurements. Ifthese conditions cannot be met, sufficient shielding must beprovided to eliminate these peaks. Shielding opposite thedetector, on the far side of the item to be assayed, will also helpto reduce the amount of ambient radiation seen by the detector(see Fig. 1).7. Sources of Error7.1 Sources of error specifically applicable to segmentedgamm
