1、Designation: C1207 10 (Reapproved 2018)Standard Test Method forNondestructive Assay of Plutonium in Scrap and Waste byPassive Neutron Coincidence Counting1This standard is issued under the fixed designation C1207; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year 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 describes the nondestructive assay ofscrap or waste for pl
3、utonium content using passive thermal-neutron coincidence counting. This test method provides rapidresults and can be applied to a variety of carefully sortedmaterials in containers as large as several thousand liters involume. The test method applies to measurements of238Pu,240Pu, and242Pu and has
4、been used to assay items whose totalplutonium content ranges from 10 mg to 6 kg (1).21.2 This test method requires knowledge of the relativeabundances of the Pu isotopes to determine the total Pu mass(Test Method C1030).1.3 This test method may not be applicable to the assay ofscrap or waste contain
5、ing other spontaneously fissioning nu-clides.1.3.1 This test method may give biased results for measure-ments of containers that include large amounts of hydrogenousmaterials.1.3.2 The techniques described in this test method havebeen applied to materials other than scrap and waste (2, 3).1.4 This t
6、est method assumes the use of shift-register-basedcoincidence technology (4).1.5 Several other techniques that are often encountered inassociation with passive neutron coincidence counting exist.These include neutron multiplicity counting (5, 6, Test MethodC1500), add-a-source analysis for matrix co
7、rrection (7), fluxprobes also for matrix compensation, cosmic-ray rejection (8)to improve precision close to the detection limit, and alterna-tive data collection electronics such as list mode data acquisi-tion. Passive neutron coincidence counting may also be com-bined with certain active interroga
8、tion schemes as in TestMethods C1316 and C1493. Discussions of these establishedtechniques are not included in this method.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 to establish appro
9、-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDev
10、elopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C986 Guide for Developing Training Programs in theNuclear Fuel Cycle (Withdrawn 2001)4C1009 Guide for Establis
11、hing and Maintaining a QualityAssurance Program forAnalytical Laboratories Within theNuclear IndustryC1030 Test Method for Determination of Plutonium IsotopicComposition by Gamma-Ray SpectrometryC1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1128 Guid
12、e for Preparation of Working Reference Materi-als for Use in Analysis of Nuclear Fuel Cycle MaterialsC1133/C1133M Test Method for Nondestructive Assay ofSpecial Nuclear Material in Low-Density Scrap and Wasteby Segmented Passive Gamma-Ray ScanningC1210 Guide for Establishing a Measurement System Qua
13、l-ity Control Program for Analytical Chemistry Laborato-ries Within the Nuclear IndustryC1316 Test Method for Nondestructive Assay of NuclearMaterial in Scrap and Waste by Passive-Active NeutronCounting Using252Cf ShufflerC1458 Test Method for Nondestructive Assay of Plutonium,Tritium and241Am by Ca
14、lorimetric Assay1This practice is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10 on NonDestructive Assay.Current edition approved April 1, 2018. Published April 2018. Originallyapproved in 1991. Last previous edition approved
15、 in 2010 as C1207 10. DOI:10.1520/C1207-10R18.2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
16、volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international
17、standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1C
18、1490 Guide for the Selection, Training and Qualification ofNondestructive Assay (NDA) PersonnelC1493 Test Method for Non-Destructive Assay of NuclearMaterial in Waste by Passive and Active Neutron Count-ing Using a Differential Die-Away System (Withdrawn2018)4C1500 Test Method for Nondestructive Ass
19、ay of Plutoniumby Passive Neutron Multiplicity CountingC1592/C1592M Guide for Making Quality NondestructiveAssay Measurements (Withdrawn 2018)4C1673 Terminology of C26.10 Nondestructive Assay Meth-ods2.2 ANSI Standards:5ANSI 15.20 Guide to Calibrating Nondestructive AssaySystemsANSI 15.36 Nondestruc
20、tive Assay Measurement Controland Assurance3. Terminology3.1 Refer to Terminology C1673 for definitions used in thistest method.4. Summary of Test Method4.1 The even mass isotopes of Pu fission spontaneously. Onthe average, two or more prompt neutrons are emitted perfission event. The number of time
21、 correlated or coincidentneutrons detected by the instrument is related to the effectivemass of240Pu, meff, present in the time. The effective240Pumass is a weighted sum of the even mass isotopes of Pu in theassay item. The total Pu mass is determined from the knownplutonium isotopic ratios and the
22、measured quantity meff.4.2 The shift register technology is intended to correct forthe effects of Accidental neutron coincidences which resultfrom the registration of neutrons in the coincidence gate whichare not correlated in time to the neutron which triggered theinspection of the gate.4.3 Other f
23、actors which may affect the assay are neutron selfmultiplication, matrix components with large (, n) reactionrates, neutron absorbers, or moderators. Corrections for theseeffects are often not possible from the measurement data alone,consequently assay items are commonly sorted into materialcategori
24、es or additional information is sometimes used.4.4 Corrections are typically made for electronic deadtimeand neutron background.4.5 Calibrations are typically based on measurements ofwell documented and appropriate reference materials. Model-ing based on knowledge of the instrument design and thephy
25、sical principles of neutron interactions may also be applied.4.6 This method includes measurement control tests toverify reliable and stable performance of the instrument.5. Significance and Use5.1 This test method is useful for determining the plutoniumcontent of scrap and waste in containers rangi
26、ng from smallcans with volumes of the order of a mL to crates and boxes ofseveral thousand liters in volume. A common applicationwould be to 208-L (55-gal) drums. Total Pu content rangesfrom 10 mg to 6 kg (1). The upper limit may be restricteddepending on specific matrix, calibration material, criti
27、calitysafety, or counting equipment considerations.5.2 This test method is applicable for U.S. Department ofEnergy shipper/receiver confirmatory measurements (9),nuclear material diversion detection, and International AtomicEnergy Agency attributes measurements (10).5.3 This test method should be us
28、ed in conjunction with ascrap and waste management plan that segregates scrap andwaste assay items into material categories according to some orall of the following criteria: bulk density, the chemical forms ofthe plutonium and the matrix, americium to plutonium isotopicratio, and hydrogen content.
29、Packaging for each categoryshould be uniform with respect to size, shape, and compositionof the container. Each material category might require calibra-tion standards and may have different Pu mass limits.5.4 Bias in passive neutron coincidence measurements isrelated to item size and density, the ho
30、mogeneity and compo-sition of the matrix, and the quantity and distribution of thenuclear material. The precision of the measurement results isrelated to the quantity of nuclear material, the (,n) reactionrate, and the count time of the measurement.5.4.1 For both benign matrix and matrix specificmea
31、surements, the method assumes the calibration referencematerials match the items to be measured with respect to thehomogeneity and composition of the matrix, the neutronmoderator and absorber content, and the quantity of nuclearmaterial, to the extent they affect the measurement.5.4.2 Measurements o
32、f smaller containers containing scrapand waste are generally more accurate than measurements oflarger items.5.4.3 It is recommended that where feasible measurementsbe made on items with homogeneous contents. Heterogeneityin the distribution of nuclear material, neutron moderators, andneutron absorbe
33、rs have the potential to cause biased results.5.5 The coincident neutron production rates measured bythis test method are related to the mass of the even numberisotopes of plutonium. If the relative abundances of theseisotopes are not accurately known, biases in the total Pu assayvalue will result.5
34、.6 Typical count times are in the range of 300 to 3600 s.5.7 Reliable results from the application of this methodrequire training of the personnel who package the scrap andwaste prior to measurement and of personnel who perform themeasurements. Training guidance is available from ANSI15.20, Guides C
35、986, C1009, C1068, and C1490.6. Interferences6.1 Conditions affecting measurement uncertainty includeneutron background, moderators, multiplication, (, n) rate,absorbers, matrix and nuclear material heterogeneity, and othersources of coincident neutrons. It is usually not possible todetect these pro
36、blems or to calculate corrections for these5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.C1207 10 (2018)2effects from the measurement data alone. Consequently, assayitems are sorted into material categories defined on t
37、he basis ofthese effects.6.2 Neutron background levels from external sources shouldbe kept as low and as constant as practical. Corrections can bemade for the effects of high-neutron background levels, butthese will adversely affect measurement precision and detec-tion limits.6.3 Neutron moderation
38、by low atomic mass materials willnot only increase thermal-neutron absorption effects, but willalso increase multiplication effects. Consequently, the mea-sured neutron rates may be either smaller or larger than thosefor a nonmoderating matrix. Hydrogenous matrices contributethe most to this effect
39、(11).6.4 Both spontaneous and induced fissions produce coinci-dent neutrons. The instrument, however, cannot distinguishbetween them. Three factors that strongly affect the degree ofmultiplication are the mass of fissile material, its density, andits geometry. Increases in mass that are not accompan
40、ied bychanges in either density or geometry will result in predictablemultiplication increases that can be incorporated into thecalibration function. Localized increases in nuclear materialdensity and/or changes in the geometry are likely to causeunknown changes in multiplication and measurement bia
41、s.6.5 Neutrons from (, n) reactions are an interference biassource if they induce multiplication effects. In addition, (,n)neutrons can increase theAccidentals rate thereby affecting thestatistical precision of the assay which is based on the netcoincidence rate.6.6 Biases may result from non-unifor
42、mity in the sourcedistribution and heterogeneity in the matrix distribution.6.7 Other spontaneous fission nuclides (for example, curiumor californium) will increase the coincident neutron countrates, causing an overestimation of the plutonium content.6.8 Cosmic rays, which are difficult to shield ag
43、ainst, canproduce coincident neutrons. Cosmic ray effects become largerfor small quantities of Pu in the presence of large quantities ofrelatively high atomic number materials, for example, iron orlead are more prolific producers than celluloxic wastes (see12.5).7. Apparatus7.1 Counting AssemblySee
44、Fig. 1.7.1.1 The apparatus used in this test method can be obtainedcommercially. Specific applications may require customizeddesign. The neutron detectors are usually3He proportionalcounters embedded in polyethylene. The detection efficiencyfor neutrons of fission energy is typically at least 15 %.
45、Largerdetection efficiencies provide better precision and lower detec-tion limits for a given count time.Ashort die-away time is alsoimportant in that it allows a shorter gate width to be used whichin turn helps control the Accidents. Ideally, the counterdetection efficiency should vary less than 10
46、 % over the itemvolume. The coincident response varies as the square of thedetection efficiency.7.1.2 Reproducible positioning of the item in the assaychamber is important for obtaining the best accuracy. Thiscounting geometry should be maintained for the measurementof all reference materials and as
47、say items. (See 11.7.)7.1.3 A 0.4 mm to 1 mm thick cadmium liner (12) is ofteninstalled on the inside surfaces of the counting chambersurrounding the assay item. This liner will reduce the die-awaytime, decrease multiplication inside the item from returningneutrons and decrease the effects on the as
48、say of neutronabsorbers inside the item. The liner will also decrease neutrondetection efficiency due to absorption of thermalized neutronsand may increase the cosmic ray spallation background. Thefinal design may represent a compromise between multipleconflicting influences.7.2 ShieldingThe detecto
49、r assembly is often surroundedby cadmium and an additional layer of hydrogenous material(see Fig. 1). Approximately 100 mm of polyethylene canreduce the neutron background in the assay chamber byapproximately a factor of 10 (13).7.3 ElectronicsHigh-count-rate nuclear electronics pro-vide a standard logic pulse from the3He proportional counters.These pulses are processed by the shift-register coincidencetechnology.7.4 Data acquisition and reduction can be facilitated byinterfacing the instrument to a computer.8. Hazards8.1 Safety HazardsConsult qualified professionals asnee
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