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首页 ASTM C1207 – 97

ASTM C1207 – 97.pdf

ASTM C1207 – 97

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简介:本文档为《ASTM C1207 – 97pdf》,可适用于工程科技领域

Designation:C–StandardTestMethodforNondestructiveAssayofPlutoniuminScrapandWastebyPassiveNeutronCoincidenceCountingThisstandardisissuedunderthefixeddesignationCthenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevisionAnumberinparenthesesindicatestheyearoflastreapprovalAsuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapprovalScopeThistestmethoddescribesthenondestructiveassayofscraporwasteforplutoniumcontentusingpassivethermalneutroncoincidencecountingThistestmethodprovidesrapidresultsandcanbeappliedtoavarietyofcarefullysortedmaterialsincontainersaslargeasLdrumsThetestmethodappliestomeasurementsofPu,Pu,andPuandhasbeenusedtoassayitemswhosetotalplutoniumcontentrangesfromtog()ThistestmethodrequiresknowledgeoftherelativeabundancesoftheplutoniumisotopestodeterminethetotalplutoniummassThistestmethodmaynotbeapplicabletotheassayofscraporwastecontainingotherspontaneouslyfissioningnuclidesThistestmethodmaygivebiasedresultsformeasurementsofcontainersthatincludelargeamountsofhydrogenousmaterialsThetechniquesdescribedinthistestmethodhavebeenappliedtomaterialsotherthanscrapandwaste(,)Thistestmethodassumestheuseofshiftregisterbasedcoincidencetechnology()SeveralothertechniquesthatarerelatedtopassiveneutroncoincidencecountingareunderdevelopmentTheseincludeneutronmultiplicitycounting(,),addasourceanalysis(),andcosmicrayrejection()DiscussionsofthesetechniquesarenotincludedinthismethodThisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuseItistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouseReferencedDocumentsASTMStandards:CTerminologyRelatingtoNuclearMaterialsCGuideforDevelopingTrainingProgramsintheNuclearFuelCycleCGuideforEstablishingaQualityAssuranceProgramforAnalyticalChemistryLaboratoriesWithintheNuclearIndustryCTestMethodforDeterminationofPlutoniumIsotopicCompositionbyGammaRaySpectrometryCGuideforQualificationofMeasurementMethodsbyaLaboratoryWithintheNuclearIndustryCGuideforthePreparationofWorkingReferenceMaterialsforUseintheAnalysisofNuclearFuelCycleMaterialsCStandardTestMethodforNDAofSpecialNuclearMaterialinLowDensityScrapandWastebySegmentedPassiveGammaRayScanningCGuideforEstablishingCalibrationforaMeasurementMethodUsedtoAnalyzeCycleMaterialsCGuideforEstablishingaMeasurementSystemQualityControlProgramforAnalyticalChemistryLaboratorieswithintheNuclearIndustryCGuideforPreparingandInterpretingPrecisionandBiasStatementsinTestMethodStandardsUsedintheNuclearIndustryANSIStandards:ANSIGuidetoCalibratingNondestructiveAssaySystemsANSIGuidetoPreparingCalibrationMaterialsforNDASystemsthatCountPassiveGammaRaysANSINondestructiveAssayMeasurementControlandAssuranceTerminologyThefollowingdefinitionsareneededinadditiontothosepresentedinASTMCDefinitions:(a,n)reactionsoccurwhenenergeticalphaparticlescollidewithlowatomicnumbernuclei,suchasO,F,orMg,producingsingleneutronscoincidenceGateLengththetimeintervalfollowingthedetectionofaneutronduringwhichadditionalneutronsareconsideredtobeincoincidencewiththeoriginalneutronThispracticeisunderthejurisdictionofASTMCommitteeConNuclearFuelCycleandisthedirectresponsibilityofSubcommitteeConNondestructiveAssayCurrenteditionapprovedJune,PublishedAugustOriginallypublishedasC–LastpreviouseditionC–TheboldfacenumbersinparenthesesrefertothelistofreferencesattheendofthistestmethodAnnualBookofASTMStandards,VolAvailablefromAmericanNationalStandardsInstitute,WndSt,thFloor,NewYork,NYCopyright©ASTM,BarrHarborDrive,WestConshohocken,PA,UnitedStatesNOTICE:ThisstandardhaseitherbeensupercededandreplacedbyanewversionordiscontinuedContactASTMInternational(wwwastmorg)forthelatestinformationcoincidentneutronstwoormoreneutronsemittedsimultaneouslyfromasingleevent,suchasfromanucleusduringfissionDie–awaytimetheaveragelifetimeoftheneutronpopulationasmeasuredfromthetimeofemissiontodetection,escape,orabsorptionTheaveragelifetimeisthetimerequiredfortheneutronpopulationtodecreasebyafactorofeItisafunctionofseveralparametersincludingchamberdesign,detectordesign,assayitemcharacteristics,andneutronenergyitemanitemreferstotheentirescraporwastecontainerbeingmeasuredanditscontentsmatrixthematerialwhichcomprisesthebulkoftheitem,exceptforthespecialnuclearmaterialandthecontainerThisisthematerialinwhichthespecialnuclearmaterialisembeddedbenignmatrixamatrixthathasnegligibleeffectsonneutrontransportAbenignmatrixincludesverylittleneutronmoderatormatrix–specificcalibrationusesacalibrationmatrixsimilartothematrixtobemeasuredNomatrixcorrectionfactorsareusedThiscalibrationisgenerallynotappropriateforothermatricesneutronabsorbersmaterialswhichhaverelativelylargethermalneutronabsorptioncrosssectionsAbsorberswiththelargestcrosssectionsarecommonlyknownasneutronpoisonsSomeexamplesarelithium,boron,cadmium,andgadoliniumneutronmoderatorsmaterialswhichslowdownneutronsthroughelasticscatteringMaterialscontaininglargeamountsoflowatomicweightmaterials,eghydrogenarehighlymoderatingpassiveneutroncoincidencecountingatechniqueusedtomeasuretherateofcoincidentneutronemissionintheassayitemTheterminologyusedinthistestmethodrefersspecificallytoshiftregisterelectronics(,)FigshowstheprobabilityofdetectinganeutronasafunctionoftimeandillustratesthetimeintervalsdiscussedShiftregisterbasedcoincidencecircuitanelectroniccircuitfordeterminingtotalst,realsplusaccidentals(ra),andaccidentals(a)inaselectedcounttimet(,)ShiftregisterbasedcircuitrywasdevelopedtoreducedeadtimesinthermalneutroncoincidencecountersThistechniquepermitsimprovedmeasurementprecisionandoperationathighercountrate($kHz)totalstthetotalnumberofneutronsdetectedduringthecounttimeThisisameasuredquantityrealsplusaccidents,(ra)thenumberofneutronsdetectedinthe(ra)gateperiod(Fig)followingtheinitialdetectionofeachneutronThisisameasuredquantityduringthecounttime(,)accidentals,(a)thenumberofneutronsdetectedinthe(a)gateperiod(Fig)followingtheinitialdetectionofeachneutronduringtheselectedcounttimetThisisameasuredquantity(,)Reals,(r)Thisquantityisthedifferencebetweenthe(ra)and(a)quantities(,)ItisproportionaltothenumberoffissionsinthesampleNeutronmultiplicationMultiplicationtakesplacewhenaneutroninteractionyieldsmorethanoneneutronasaproductInducedfissionistheprimarymechanismforneutronmultiplication,however(n,n)interactionsarealsomultiplicationeventspoissonassumptionForpassiveneutroncoincidencemeasurements,itisassumedthatthenetcountsinafixedperiodoftimefollowaPoissondistributionThisassumptioncanbeverifiedbycomparingtheobservedstandarddeviationofaseriesofmeasurementsonanitemwiththesquarerootoftheaveragenumberofcountsIfthePoissonassumptioniscorrect,thesenumbersshouldbeequalwithinrandomerrorPrecisionTheprecisionofameasurementistakenNOTECurve(a)isasimplifiedprobabilitydistributionshowingtheapproximatelyexponentialdecay,asafunctionoftime,fordetectingasecondneutronfromasinglefissioneventTheprobabilityfordetectingarandomneutronisconstantwithtimeTypicalcoincidencetimingparametersareshownin(b)FIGProbabilityofDetectionasaFunctionofTimeCNOTICE:ThisstandardhaseitherbeensupercededandreplacedbyanewversionordiscontinuedContactASTMInternational(wwwastmorg)forthelatestinformationtobethestandarddeviationor(percent)relativestandarddeviationofaseriesofmeasurementstakenonthesameitemunderessentiallythesameconditionsPredelaythecoincidencecircuithasapredelayimmediatelyafteraneutronhasbeendetectedtoallowtheamplifierstorecoverandpreparetodetectsubsequentneutronsThisprincipleisshowninFigPueffectivemass,meffisthemassofPuthatwouldproducethesamecoincidentneutronresponseintheinstrumentastheassayitemItiscorrelatedtothequantityofevenmassisotopesofplutoniumintheassayitem()transuranicwaste(TRUwaste)asdefinedinDOEOrder(),transuranicwasteisradioactivewastecontainingalphaemittingisotopeswithatomicnumbergreaterthanandhalflifegreaterthanyears,andwithactivityconcentrationsgreaterthannCipergramofwasteatthetimeofthemeasurementSummaryofTestMethodTheevenmassisotopesofplutoniumfissionspontaneouslyOntheaverage,twoormoreneutronsareemittedperfissioneventThenumberofthesecoincidentneutronsdetectedbytheinstrumentiscorrelatedtothequantityofevenmassisotopesofplutoniumintheassayitem,meffThetotalplutoniummassisdeterminedfromtheknownplutoniumisotopicratiosandthemeasuredquantityofevenmassisotopesTheshiftregistertechnologyisintendedtocorrectfortheeffectsofaccidentalneutronsOtherfactorswhichmayaffecttheassayaremultiplicationandmatrixcomponentswithlarge(a,n)reactionrates,neutronabsorbers,ormoderatorsCorrectionsfortheseeffectsareoftennotpossiblefromthemeasurementdataalone,consequentlyassayitemsaresortedintomaterialcategoriesoradditionalinformationisusedtoobtainthebestassayresultCorrectionsaretypicallymadeforelectronicdeadtimeandneutronbackgroundCalibrationsarebasedonmeasurementsofwelldocumentedandappropriatereferencematerialsThismethodincludesmeasurementcontrolteststoverifyreliableandstableperformanceoftheinstrumentSignificanceandUseThistestmethodisusefulfordeterminingtheplutoniumcontentofscrapandwasteincontainersaslargeasL(gal)drumsTotalplutoniumcontentrangesfrommgtokg()Theupperlimitmayberestrictedtosmallermassvaluesdependingonspecificmatrix,calibrationmaterial,criticalitysafety,orcountingequipmentconsiderationsThistestmethodisapplicableforUSDepartmentofEnergyshipperreceiverconfirmatorymeasurements(),nuclearmaterialdiversiondetection,andInternationalAtomicEnergyAgencyattributesmeasurements()Thistestmethodshouldbeusedinconjunctionwithascrapandwastemanagementplanthatsegregatesscrapandwasteassayitemsintomaterialcategoriesaccordingtosomeorallofthefollowingcriteria:bulkdensity,thechemicalformsoftheplutoniumandthematrix,americiumtoplutoniumisotopicratio,andhydrogencontentPackagingforeachcategoryshouldbeuniformwithrespecttosize,shape,andcompositionofthecontainerEachmaterialcategorywillrequirecalibrationstandardsandmayhavedifferentplutoniummasslimitsBiasinpassiveneutroncoincidencemeasurementsisrelatedtoitemsizeanddensity,thehomogeneityandcompositionofthematrix,andthequantityanddistributionofthenuclearmaterialTheprecisionofthemeasurementresultsisrelatedtothequantityofnuclearmaterial,the(a,n)reactionrate,andthecounttimeofthemeasurementForbothbenignmatrixandmatrixspecificmeasurements,themethodassumesthecalibrationreferencematerialsmatchtheitemstobemeasuredwithrespecttothehomogeneityandcompositionofthematrix,theneutronmoderatorandabsorbercontent,andthequantityofnuclearmaterial,totheextenttheyaffectthemeasurementMeasurementsofsmallercontainerscontainingscrapandwastearegenerallymoreaccuratethanmeasurementsofL(gal)drumsItisrecommendedthatmeasurementsbemadeonitemswithhomogeneouscontentsHeterogeneityinthedistributionofnuclearmaterial,neutronmoderators,andneutronabsorbershavethepotentialtocausebiasedresultsThecoincidentneutronproductionratesmeasuredbythistestmethodareproportionaltothemassoftheevennumberisotopesofplutoniumIftherelativeabundancesoftheseisotopesarenotaccuratelyknown,biasesinthetotalplutoniumassayvaluewillresultAtypicalcounttimeissecondsReliableresultsfromtheapplicationofthismethodrequiretrainingofthepersonnelwhopackagethescrapandwastepriortomeasurementandofpersonnelwhoperformthemeasurementsTrainingguidanceisavailablefromANSI,ASTMC,ASTMC,andASTMCInterferencesConditionsaffectingmeasurementuncertaintyincludeneutronbackground,moderators,multiplication,large(a,n)rates,absorbers,matrixandnuclearmaterialheterogeneity,andothersourcesofcoincidentneutronsItisusuallynotpossibletodetecttheseproblemsortocalculatecorrectionsfortheseeffectsfromthemeasurementdataaloneConsequently,assayitemsaresortedintomaterialcategoriesdefinedonthebasisoftheseeffectsNeutronbackgroundlevelsfromexternalsourcesshouldbekeptaslowandasconstantaspracticalCorrectionscanbemadefortheeffectsofhighneutronbackgroundlevels,butthesewilladverselyaffectmeasurementprecisionanddetectionlimitsNeutronmoderationbylowatomicmassmaterialswillnotonlyincreasethermalneutronabsorptioneffects,butwillalsoincreasemultiplicationeffectsConsequently,themeasuredneutronratesmaybeeithersmallerorlargerthanthoseforanonmoderatingmatrixHydrogenousmatricescontributethemosttothiseffect()BothspontaneousandinducedfissionsproducecoincidentneutronsTheinstrument,however,cannotdistinguishbetweenthemThreefactorsthatstronglyaffectthedegreeofmultiplicationarethemassoffissilematerial,itsdensity,anditsgeometryIncreasesinmassthatarenotaccompaniedbyCNOTICE:ThisstandardhaseitherbeensupercededandreplacedbyanewversionordiscontinuedContactASTMInternational(wwwastmorg)forthelatestinformationchangesineitherdensityorgeometrywillresultinpredictablemultiplicationincreasesthatcanbeincorporatedintothecalibrationfunctionLocalizedincreasesinnuclearmaterialdensityandorchangesinthegeometryarelikelytocauseunknownchangesinmultiplicationandmeasurementbiasNeutronsfrom(a,n)reactionsareaninterference(bias)sourceiftheyinducemultiplicationeffectsInaddition,(a,n)neutronscanincreaseheaccidentalratetherebyaffectingthestatisticalprecisionoftheassayBiasesmayresultfromnonuniformityinthesourcedistributionandheterogeneityinthematrixdistributionOtherspontaneousfissionnuclides(forexample,curiumorcalifornium)willincreasethecoincidentneutroncountrates,causinganoverestimationoftheplutoniumcontentCosmicrays,whicharedifficulttoshieldagainst,canproducecoincidentneutronsCosmicrayeffectsbecomelargerforsmallquantitiesofplutoniuminthepresenceoflargequantitiesofhighatomicnumbermaterials,forexample,iron(see)ApparatusCountingAssemblySeeFigTheapparatususedinthistestmethodcanbeobtainedcommerciallySpecificapplicationsmayrequirecustomizeddesignTheneutrondetectorsareusuallyHeproportionalcountersembeddedinpolyethyleneThedetectionefficiencyforneutronsoffissionenergyshouldbeatleastLargerdetectionefficienciesprovidebetterprecisionandlowerdetectionlimitsforagivencounttimeIdeally,thecounterdetectionefficiencyshouldvarylessthanovertheitemvolumeReproduciblepositioningoftheiteminthechamberisimportantforobtainingthebestaccuracyThiscountinggeometryshouldbemaintainedforthemeasurementofallreferencematerialsandassayitems(See)Ammtommthickcadmiumliner()isofteninstalledontheinsidesurfacesofthecountingchambersurroundingtheassayitemThislinerwilldecreasemultiplicationinsidetheitemanddecreasetheeffectsofneutronabsorbersinsidetheitemThelinerwillalsodecreaseneutrondetectionefficiencyduetoabsorptionofthermalizedneutronsandmayincreasethecosmicrayspallationbackgroundShieldingThedetectorassemblyshouldbesurroundedbycadmiumandanadditionallayerofhydrogenousmaterial(seeFig)Fourinchesofpolyethylenecanreducetheneutronbackgroundinthesamplechamberbyapproximatelyafactorof()ElectronicsHighcountratenuclearelectronicsprovideastandardlogicpulsefromtheproportionalcountersThesepulsesareprocessedbytheshiftregistercoincidencetechnologyDataacquisitionandreductioncanbefacilitatedbyinterfacingtheinstrumenttoacomputerHazardsSafetyHazardsConsultqualifiedprofessionalsasneededPrecautionsshouldbetakentopreventinhalation,ingestion,orthespreadofplutoniumcontaminationduringwasteorscraphandlingoperationsAllcontainersshouldbesurveyedonaregularbasiswithanappropriatemonitoringdevicetoverifytheircontinuedintegrityPrecautionsshouldbetakentominimizepersonnelexposuretoradiationPrecautionsshouldbetakenregardingnuclearcriticality,especiallyofunknownitemsThemeasurementchamberapproximatesareflectinggeometryforfastneutronsTheassumptionthatwasteisnotofcriticalityconcernisnotrecommendedCountingchambersmaycontainacadmiumlinerPrecautionsshouldbetakentopreventtheinhalationoringestionofcadmiumItisaheavymetalpoisonCadmiumshieldingshouldbecoveredwithnontoxicmaterialsPrecautionsshouldbetakentoavoidcontactwithhighvoltageTheHetubesrequirelowcurrent,highvoltage,powersuppliesTheweightoftheinstrumentmayexceedfacilityfloorloadingcapacitiesCheckforadequatefloorloadingcapacitybeforeinstallationTechnicalHazards:LocatetheinstrumentinanareaoflowneutronbackgroundProhibitthemovementofradioactivematerialinhevicinityoftheinstrumentwhileameasurementisinprogressUtilizingameasurementresultoutsideofthecalibrationrangeshouldbecarefullyevaluatedand,ingeneral,isnotrecommendedUtil

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