ASTM C1316-2008 Standard Test Method for Nondestructive Assay of Nuclear Material in Scrap and Waste by Passive-Active Neutron Counting Using 252Cf Shuffler《使用a252Cf的被动-主动中子计数法在碎片和.pdf

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1、Designation: C 1316 08Standard Test Method forNondestructive Assay of Nuclear Material in Scrap andWaste by Passive-Active Neutron Counting Using252CfShuffler1This standard is issued under the fixed designation C 1316; the number immediately following the designation indicates the year oforiginal ad

2、option 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 covers the nondestructive assay ofscrap and waste ite

3、ms for U, Pu, or both, using a252Cf shuffler.Shuffler measurements have been applied to a variety of matrixmaterials in containers of up to several 100 L. Corrections aremade for the effects of matrix material.Applications of this testmethod include measurements for safeguards, accountability,TRU, a

4、nd U waste segregation, disposal, and process controlpurposes (1, 2, 3).21.1.1 This test method uses passive neutron coincidencecounting (4) to measure the240Pu-effective mass. It has beenused to assay items with total Pu contents between 0.03 g and1000 g. It could be used to measure other spontaneo

5、uslyfissioning isotopes such as Cm and Cf. It specifically describesthe approach used with shift register electronics; however, itcan be adapted to other electronics.1.1.2 This test method uses neutron irradiation with amoveable Cf source and counting of the delayed neutrons fromthe induced fissions

6、 to measure the235U equivalent fissilemass. It has been used to assay items with235U contentsbetween 0.1 g and 1000 g. It could be used to assay other fissileand fissionable isotopes.1.2 This test method requires knowledge of the relativeisotopic composition (See Test Method C 1030) of the specialnu

7、clear material to determine the mass of the different elementsfrom the measurable quantities.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 The techniques described in this test method have beenapplied to materials othe

8、r than scrap and waste. These otherapplications are not addressed in this test method.1.5 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-priate safety and health practices a

9、nd determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:3C 1009 Guide for Establishing a Quality Assurance Pro-gram for Analytical Chemistry Laboratories Within theNuclear IndustryC 10

10、30 Test Method for Determination of Plutonium Isoto-pic Composition by Gamma-Ray SpectrometryC 1068 Guide for Qualification of Measurement Methodsby a Laboratory Within the Nuclear IndustryC 1128 Guide for Preparation of Working Reference Mate-rials for Use in the Analysis of Nuclear Fuel CycleMater

11、ialsC 1133 Test Method for Nondestructive Assay of SpecialNuclear Material in Low-Density Scrap and Waste bySegmented Passive Gamma-Ray ScanningC 1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC 1207 Test Method for NondestructiveAssay

12、of Plutoniumin Scrap and Waste by Passive Neutron CoincidenceCountingC 1210 Guide for Establishing a Measurement SystemQuality Control Program for Analytical Chemistry Labo-ratories Within the Nuclear IndustryC 1215 Guide for Preparing and Interpreting Precision andBias Statements in Test Method Sta

13、ndards Used in theNuclear IndustryC 1490 Guide for the Selection, Training and Qualificationof Nondestructive Assay (NDA) PersonnelC 1592 Guide for Nondestructive Assay MeasurementsC 1673 Terminology of C26.10 Nondestructive AssayMethods1This test method is under the jurisdiction ofASTM Committee C2

14、6 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10 on NonDestructive Assay.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1995. Last previous edition approved in 2001 as C 1316 01.2The boldface numbers in parentheses refer to a list of r

15、eferences 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 volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Inter

16、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 ANSI Documents:ANSI 15.20 Guide to Calibrating Nondestructive AssaySystems4ANSI N15.36 Nondestructive Assay Measurement Controland Assurance43. Terminology3.1 DefinitionsTerms shall be defined in accord

17、ance withTerminology C 1673.3.2 Definitions of Terms Specific to This Standard:3.2.1 active mode, ndetermines total fissile mass in theassayed item through neutron interrogation and counting of thedelayed neutrons from induced fissions.4. Summary of Test Method4.1 This test method consists of two di

18、stinct modes ofoperation: passive and active. The instrument that performs theactive mode measurement is referred to as a shuffler due to thecyclic motion of the252Cf source. This test method usuallyrelies on passive neutron coincidence counting to determine thePu content of the item, and active neu

19、tron irradiation followedby delayed neutron counting to determine the U content.4.1.1 Passive Neutron Coincidence Counting ModeTheeven mass isotopes of Pu fission spontaneously. On averageapproximately 2.2 prompt neutrons are emitted per fission. Thenumber of coincident fission neutrons detected by

20、the instru-ment is correlated to the quantity of even mass isotopes of Pu.The total Pu mass is determined from the known isotopic ratiosand the measured quantity of even mass isotopes. This testmethod refers specifically to the shift register coincidencecounting electronics (see (4) and Test Method

21、C 1207).4.1.2 Active Neutron (Shuffler) ModeFissionsin235U,239Pu and other fissile nuclides can be induced bybombarding them with neutrons. Approximately 1 % of theneutrons emitted per fission are delayed in time, being emittedfrom the fission products over the time range from s to severalminutes af

22、ter the fission event. Roberts et. al (5) were the firstto observe delayed neutron emission. We now know that over270 delayed neutron precursors contribute to the yield althoughthe time behavior can be adequately described for mostpurposes using a few (six to eight) effective groups each witha chara

23、cteristic time constant. The idea of detecting delayedneutrons for the analysis of235U has been attributed to Echoand Turk (6). The active shuffler mode consists of severalirradiate-count cycles, or shuffles, of the252Cf neutron sourcebetween the positions illustrated in Fig. 1.252Cf emits a fission

24、neutron spectrum. During each shuffle, the252Cf source ismoved close to the item for a short irradiation, then moved toa shielded position while the delayed neutrons are counted. Thenumber of delayed neutrons detected is correlated with thequantity of fissile and fissionable material. The total U ma

25、ss isdetermined from the known relative isotopic compostion andthe measured quantity of235U equivalent (7).4.2 Either corrections are made for the effects of neutronabsorbers and moderators in the matrix, or a matrix-specificcalibration is used. The effect that needs correction is theincrease or dec

26、rease in the specific neutron signal caused by thematrix.4.3 Corrections are made for deadtime, neutron background,and the Cf source decay.4.4 The active mode also induces fissions in Pu if it ispresent in the assay item. The passive measurement of Pu canbe used to correct the active measurement of2

27、35U effective forthe presence of Pu.4.5 Calibrations are generally based on measurements ofwell documented reference materials (8) and may be extendedby calculation (9-11). The method includes measurementcontrol tests to verify reliable and stable performance of theinstrument.5. Significance and Use

28、5.1 This test method is used to determine the U and Pucontent of scrap and waste in containers. Active measurementtimes have typically been 100 to 1000 s. Passive measurementtimes have typically been 400 s to several hours. The followinglimits may be further restricted depending upon specificmatrix,

29、 calibration material, criticality safety, or countingequipment considerations.5.1.1 The passive measurement has been applied to benignmatrices in 208 L drums with Pu content ranging from 30 mgto 1 kg.5.1.2 The active measurement has been applied to wastedrums with235U content ranging from about 100

30、 mg to 1 kg.5.2 This test method can be used to demonstrate compliancewith the radioactivity levels specified in safeguards, waste,disposal, and environmental regulations (for example, see NRCregulatory guides 5.11, 5.53, DOE Order 5820.2a, and10CFR61 sections 61.55 and sections 61.56, 40CFR191, and

31、DOE/WIPP-069).5.3 This test method could be used to detect diversionattempts that use shielding to encapsulate nuclear material.5.4 The bias of the measurement results is related to theitem size and density, the homogeneity and composition of thematrix, and the quantity and distribution of the nucle

32、ar mate-rial. The precision of the measurement results is related to thequantity of nuclear material and the count time of the mea-surement.5.4.1 For both the matrix-specific and the matrix-correctionapproaches, the method assumes the calibration materialsmatch the items to be measured with respect

33、to the homoge-neity and composition of the matrix, the neutron moderator andabsorber content, and the quantity of nuclear material, to theextent they affect the measurement.5.4.2 It is recommended that measurements be made onsmall containers of scrap and waste before they are combinedin large contai

34、ners. Special arrangement may be required toassay small containers to best effect in a large cavity generalpurpose shuffer.5.4.3 It is recommended that measurements be made oncontainers with homogeneous contents. In general, heteroge-neity in the distribution of nuclear material, neutron modera-tors

35、, and neutron absorbers has the potential to cause biasedresults.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.C1316082NOTE 1The shuffler measurement consists of several cycles. Each cycle includes the movement of the25

36、2Cf source from the storage (or home)position to the irradiation position close to the item, irradiation of the item for a period of about 10 s, return of the source to the shield followed by acounting period of about 10 s. In obvious notation this cycle structure may be succinctly described by the

37、four time periods involved (tin,tirr,tout,tcnt).Typically the one-way transit times are less than 1 s.FIG. 1 Cf Shuffler Measurement PrincipleC13160835.5 This test method requires that the relative isotopiccompositions of the contributing elements are known.5.6 This test method assumes that the dist

38、ribution of thecontributing isotopes is uniform throughout the container whenthe matrix affects neutron transport.5.7 This test method assumes that lump affects areunimportantthat is to say that large quantities of specialnuclear material are not concentrated in a small portion of thecontainer.5.8 F

39、or best results from the application of this test method,appropriate packaging of the items is required. Suitable train-ing of the personnel who package the scrap and waste prior tomeasurement should be provided (for example, seeANSI 15.20, Guide C 1009, Guide C 1490, and Guide C 1068for training gu

40、idance). Sometimes site specific conditions andrequirements may have greater bearing.6. Interferences6.1 Potential sources of measurement interference includeunexpected nuclear material contributing to the active orpassive neutron signal, self-shielding by lumps of fissilematerial, neutron self-mult

41、iplication, excessive quantities ofabsorbers or moderators in the matrix, heterogeneity of thematrix, and the non-uniformity of the nuclear material spatialdistribution especially within a moderating matrix. In general,the greatest potential source of bias for active neutron mea-surement is heteroge

42、neity of the nuclear material within ahighly moderating matrix, while the greatest for passiveneutron measurement is neutron moderation and absorption(12).6.2 The techniques described in this test method cannotdistinguish which isotope is generating the measured response.If more than one nuclide tha

43、t produces a response is present,the relative abundances and relative specific responses of thosenuclides must be known.6.2.1 Active ModeThe unidentified presence of otherfissionable nuclides will increase the delayed neutron countrate, causing an overestimation of the235U content. For ex-ample, a c

44、alibration based on highly enriched U will causebiased results if the unknowns actually contain low-enriched Udue to the potential difference in the fractional contributionarising from the fast fission in238U (13, 14).6.2.2 Passive ModeThe unidentified presence of otherspontaneous fission nuclides,

45、such as Cm and Cf, will increasethe coincident neutron rates, causing an overestimation of thePu content. The active mode measurement of Pu is generallynot sensitive to this source of bias (although counting precisionmay be affected) because the masses of concern are so smalland present a comparativ

46、ely tiny induced fission signal.6.3 Lumps of nuclear material can exhibit self-shielding ormultiplication. This effect is often larger for moderating(hydrogenous) matrices.6.3.1 Active Mode (Self-Shielding)The nuclear materialon the surface of the lump shields the inside of the lump fromthe interrog

47、ating neutrons (15, 16).6.3.2 Passive Mode (Multiplication)Neutrons originatingin the lump induce fissions in the same lump which boosts thespecific coincident rate.6.4 Moderators in the matrix can cause a bias in themeasurement results, unless a correction is made or an appro-priate matrix specific

48、 calibration is used. The magnitude anddirection of this bias depend on the quantity of moderatorpresent, the distribution of the fissile material, and the size ofthe item (2, 17).6.4.1 Although moderation is the greatest potential sourceof bias for passive measurements, the passive method isgeneral

49、ly less susceptible to the presence of moderator than theactive method.6.4.2 The presence of absorbers in the matrix can cause biasif there is sufficient moderator present. The moderator slowsfast neutrons which can then be captured more effectively bythe absorbers.6.4.3 The instrument produces a nonuniform responseacross the container, the severity varying with the concentra-tion of hydrogen in the matrix. A source at the center of thecontainer can produce either a higher or lower response thanthe same source located at the surface of the containerdepending on the item