Neutron Personnel Dosimetry

1 Page 1 NBSMeasurementServices: Neutron Personnel Dosimetry U.S.DepartmentofCommerce NationalBureauofStandards Open at page → 2 Page 2 CenterforRadiationResearch TheCenterforRadiationResearchisamajorcomponentoftheNationalMeasurementLaboratory intheNational BureauofStandards. TheCenterprovidestheNationwithstandardsandmeasurementservicesforionizing radiat... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: NEUTRONPERSONNELDOSIMETRY RobertB.Schwartz CenterforRadiationResearch NationalMeasurementLaboratory NationalBureauofStandards Gaithersburg,MD20899 U.S.DEPARTMENTOFCOMMERCE,MalcolmBaldrige,Secretar... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:87-619842 NationalBureauofStandardsSpecialPublication250-12 Natl.Bur.Stand.(U.S.),Spec.Publ.250-12,44pages(July1987) CODEN:XNBSAV Commercialproducts—materialsandinstruments—areidentifie... Open at page → 5 Page 5 PREFACE Thecalibration andrelatedmeasurement servicesoftheNationalBureau ofStandardsareintendedtoassistthemakersandusersofprecision measuringinstruments inachievingthehighestpossiblelevelsof accuracy,quality,andproductiv... Open at page → 6 Page 6 Detailedproceduresaregivenforcalibration ofneutrondosimetersandrem- meterswithcaliforniumneutronsources,both"bare"andmoderated. Correc- tionsforairscatter,room-return, anisotropicneutronemission,anddevia- tionfromtheinve... Open at page → 7 Page 7 CONTENTS 1.Description ofService 1 2.FacilityDescription 3 3.Corrections 5 a.AnisotropicEmission 5 b.RoomReturn 6 c.AirScatter 6 d.DeviationfromInverseSquareLaw 7 Procedures 7 a.Spreadsheet forDosimeterIrradiations 7 b.S... Open at page → 8 Page 8 TABLEOFCONTENTS,CONTINUED LISTOFTABLES Table 1.RoomReturnCorrection, S,percentpermeter-squared 5 Table2.AirScatterCorrection, percentpermeter 7 Table3-ValuesofGroupSourceStrengthperLogarithmicEnergy D-2 Intervalfora^^^Cf... Open at page → 9 Page 9 1.Description ofService TheNational BureauofStandards (NBS)suppliesessentially "free-field" neutronirradiations forcalibratingneutrondetectioninstrumentation. This isdoneunderSP250NumberiJ4060C(formerly 8.1J)^. By"free-f... Open at page → 10 Page 10 Thebasicphysicalprinciplesarestraightforward. Westartwithacalifor- niumneutronsourceofknownemission rate, Q,measured atNBS^withan uncertainty of~±1.3%. (Notethatthisuncertainty, andallotheruncer- taintiesgiveninthisdocum... Open at page → 11 Page 11 inthemaximumdoseequivalentrateformoderatedirradiations bythepresent californium sourcestrengthandbythefactthattherearespectralchanges atclosedistances (<30cm)^''°whichlimittheminimumdistancewhichcan beused. Weplan,howeve... Open at page → 12 Page 12 FIG.1SimplifiedviewofLowScatterNeutronCalibrationFacility (sections ofoverheadgratingfloorshownremoved. ).Perspectivevariationallows compressedviewofwhatisvirtually alarge,nearlyemptyroom. .1Neutronsourcebeingraisedintop... Open at page → 13 Page 13 Therestofthefacilityconsistsofalowmassstandapproximately 2.1m high. Thetopofthestandisanaluminumplatform,approximately 60cmx60 cmX6mmthick,tosupporttheinstruments tobeirradiated. Thestandis oncasterswhichrideonangleirons... Open at page → 14 Page 14 3.b.RoomReturn Ithasbeenshown^^'^^ thatroomscatteredneutronsareessentiallyuniformly distributed throughout theroom,andsincethefluenceofsourceneutrons variesas 1/r^ ,ifwefirstcorrectforairscattering (see3.c.),wecan,in gen... Open at page → 15 Page 15 Table2-AirScatterCorrection,percentpermeter Device Bare Moderated 3"Sphere AlbedoDosimeter Remmeter NTAFilm,TrackEtchDosimeter 1.1% 1. 1 1.0 0.5 3.0 2.3 0.9 3.d.DeviationfromInverseSquareLaw Forasphericaldetectorandapoin... Open at page → 16 Page 16 nentrecord. Thisspreadsheet isthenusedasatemplateforthenextdosim- eterirradiation. Onedoesnotlayoutanewspreadsheet foreachnew calibration. ) DOSIhETER IRRADIATIONS January30.1985 Source Q(n/s) D(cm) NS-865.477e+08 50.8 N... Open at page → 17 Page 17 andforNS-79 ,abaresource, FFDE^ =.00954*Q/D^ (6) bare wherethenumerical factorsarethefluence-to-dose equivalent conversion factorsdiscussed inSection 1 . Thecorrection(percent)forthemoderatedsource(NS-86) is CORRECTION(?... Open at page → 18 Page 18 4.b.Spreadsheet forRemmeterIrradiation Remmetercalibrations arequitedifferentfromdosimetercalibrations. For onething,inthelattercaseoneneverseestheresults. Thedosimetersare irradiated andsentbacktotheownerwhotakescareoft... Open at page → 19 Page 19 PRS-2 S/N348 CalvertCliffs Test237140 runSource Q(n/s) D(cm)FFDE D'(cm)Corr ReadCRead CalF 1 136-z 4.959e+06 60 3.17 33 . 3 4.8 4.38 4.18 0.76 2 NS-39 5.007e+07 60 ol. 33.3 4.8 44.4 42.3 0.76 3 NS-86 3.977e+08 60 254.1 3... Open at page → 20 Page 20 themagnitudeofthefluctuations, andestimatesthelavalueofthesefluc- tuations(seep.14),whichisthentakentobethestatisticaluncertainty. Withadigitalreadout,severalreadings(typically, 5to8)areaveraged, usingtheprogram"AVERAG"(... Open at page → 21 Page 21 reading("CRead"), thecalibration factor("CalF"), andtheover-alluncer- taintyinthecalibrationfactor("Sum"and"Sum+^"). Similarspreadsheets havebeenprepared fortheothertypesofremmeters whichweencounter, forboththebareandmod... Open at page → 22 Page 22 thisstepisnotnecessary. TheEberlinePRS-2,thenextmostcommoninstru- ment, isdigitalanddoesnotrequirerangeswitching. Itdoes,however, haveaswitchtoselectthenumberofcountsitwillaccumulate, andhence thestatistical accuracy, fo... Open at page → 23 Page 23 "Stat", "cal", "Corr", "Dist", "Sum", and"Sum+^l" inthebottompartof Figure3aretheuncertainties expressedaspercentages. Again,alluncer- taintiesaregivenasonestandarddeviation (1o). 5.a. StatisticalUncertainty ("Stat") Thi... Open at page → 24 Page 24 anuncertainty duetoourlackofknowledgeofthelocationoftheeffective centeroftheinstrument. IthasbeenshownbyJ.B.Hunt^®thatfora spherically symmetric instrument, theeffectivepointofmeasurement canbe takenastheinstrument's geo... Open at page → 25 Page 25 Itmustbesaid,however, thatthemostimportantformofinternalquality control isjustwatching theresultscarefully astheycomein. Thisis particularly trueinthecaseofinstruments withadigitalreadout. As indicated inthe"Procedures"... Open at page → 26 Page 26 8.Acknowledgement IshouldliketothankCharlesEisenhauer forhisclosecollaboration and expertguidanceinmakingthiscalibrationserviceareality. 18 Open at page → 27 Page 27 REFERENCES 1. G.A.Uriano,E.L.Garner, R.K.KirbyandW.P.Reed,"NBSCalibration ServicesUsersGuide1986-1988," NBSSpecialPublication250,July,1986. 2. R.B.SchwartzandC.M.Eisenhauer, "TheDesignandConstruction ofa DjO-Moderated ^^... Open at page → 28 Page 28 14. R.B.SchwartzandC.M.Eisenhauer, "Procedures forCalibratingNeutron PersonnelDosimeters," NBSSpecialPublication633(1982). 15. C,M.Eisenhauer, J.B.Hunt,andR.B.Schwartz,"Calibration Tech- niquesforNeutronPersonalDosimetry... Open at page → 29 Page 29 Appendix A.PocketCalculatorPrograms ThelistingsonthefollowingpageareprogramsforHewlett-Packard Series10 calculators. Thefirstlisting,"DOSEEQUIVALENTRATE",isusedforsolvingequations (5) and(6),knowingthesourceemissionrate,... Open at page → 30 Page 30 DOSEEQUIk^LENTRATE Keystrokes Pisplay fLBLA 001-42,21,11 4 002- 4 003- 48 1 004- 1 4 005- 4 4 006- 4 007- 10 fLBLC 008-42,21,13 GSB1 009- 321 X 010- 11 gRTN 011- 4332 fLBLB 012-42,21,12 2 013- 2 014- 48 0 015- 0 3 016- 3... Open at page → 31 Page 31 AppendixB.AveragingProgram Thelistingonthenextpageisfortheprogram"AVERAG" ontheTandy200. Theuserisfirstpromptedforthenumberofinputdatapoints(line20)and thenforthemannerinwhichtheuncertainties areexpressed(lines30-70). Th... Open at page → 32 Page 32 1REM-"AVERAG.BA" 10CLEAR:CLS 20INPUT"Houjmanydatapointsarethere"iN 25DIMG(N-1 ,1 ) 30PRINT"Aretheuncertainties givenas:" 35PRINT 40PRINTTAE(2);"1.Absolutestandarddeviations?" 50PRINTTAB(2);"2. 7.S.D.isamevalueforallpoint... Open at page → 33 Page 33 590RETURN 700FORA=0TON-1 710 PRINT"NO. " ;A+1;TaE(6) 720 INPUT"Datum,'/.Uncertainty " ;D,P 730 6(A,0;=D: G(A,1)= (.01P-^D )-^-2 750 WTDT=WTDT +D*G(A,1) 760 SUMW=SUMW +G(A,1> 770NEXTA 780RETURN B-3 Open at page → 35 Page 35 Appendix C.SampleTestReports PagesC-2 -C-^areatypicalremmete showninthespreadsheet ofFigure3. byatestreportfordosimeter irrad explanatory. rtestreport,generatedfromthedata ThisisfollowedonpagesC-5andC-6 iations. Therepor... Open at page → 36 Page 36 rOMMNBS— iMCV.•-•B) U.S.DepartmentofCommerce NATIONALBUREAUOFSTANDARDS OAITHERSBURC.MARYLAND20899 REPORTOFTEST NBSTestNo. InstrumentsSubmittedby: NuclearPowerStation DatesofIrradiation: April2^,1986 NeutronSources: Calif... Open at page → 37 Page 37 ThenextcolumnsInTableII,"CorrectedInstrumentReadings"arethe remmeterreadingsfromTableI,correctedfortheneutronbackground mentionedabove. (Atthesmallestdistance,thereisalsoasmall correctionforthedeviationfromtheinversesqua... Open at page → 38 Page 38 NBSTeatNo, TABLE I -Experimental Data Distance (r) InstrumentReadings,mrem/h (center-to- SourceNo. center),cm Ser.f3^6 Ser.#355 Ser.#377 SR-Cf-132 99 11.18 3.67 H.6 SR-Cf-132 50 14.9 U.35 16.7 SR-Cf-132 25.1 56.3 56.7 65... Open at page → 39 Page 39 FORMNBS—259 (REV.e-es) U.S.DepartmentofCommerce NATIONALBUREAUOFSTANDARDS GAITHERSBURG.MARYLAND20899 REPORTOFTEST NBSTestNo. DosimetersSubmittedby: DateofIrradiation: January2,1985 DoseEquivalentDelivered: 750mrem Certif... Open at page → 40 Page 40 ever, "thedosimeters are 7cmawayfromthecenter,thedose equivalent rateatthedosimeterpositionis2%lower. Onthe otherhand,weestimatethattheairandroomscatteredneutrons willincreasethedosimeterresponsebyapproximately 4K.Thus,... Open at page → 41 Page 41 AppendixD.GraphicandTabularRepresentation oftheNeutronSpectra Thespectraarerepresented asplotsofABo/Aln(E/Eo )(linearscale)versus neutronenergyE(logarithmic scale)withABg(groupsourcestrength)normal- izedtoatotalsourcestr... Open at page → 42 Page 42 TabI*3—Valu«sofgrouptourc*ttrvnothp«rlogarithmicarwrgyintervalfora3E2Cfspontanaoutfiationtourca Nautronartargy.£ Aln(£-/£jl M«V • -' 4.14X10"' 0.01 >.4UX10 ' 0.06 2,74X10"' 0.10 1,24X10"' 0.20 3.33X10"* 0,25 X10"^ O.X 7.... Open at page → 43 Page 43 D-3 Open at page → 44 Page 44 Tabic4•VakiMofagroupaourca•trangthparlogarfthmkanargyintarvalfora^Cfapontanaouafission aouroaintl>acantraofaOjOapharawitharadiusof180mm Nautronanargy.£ M«V »- 1 4.14X 10-T 1,0Xto-« 2.15X10-2 1.0Xio-» 2.74X10-2 6.0X10-8 3... Open at page → 45 Page 45 D-5 Open at page → 47 Page 47 Appendix E.Definitions Takenfrom: NCRPReportNo.51 ,"RadiationProtectionDesignGuide- linesfor0.1-100MeVParticleAccelerator Facilities". National CouncilonRadiationProtection andMeasurements, Washington, D.C. (March,1977).... Open at page → 48 Page 48 NBS-n4A(REV.2.ec) U.S.DEPT.OFCOMM. 1.PUBLICATIONOR 2.PerformingOrgan.ReportNo.3.PublicationDate BIBLIOGRAPHICDATA REPORTNO. July1987 SHEET(Seeinstructions) NBS/SP-250/12 4.TITLEANDSUBTITLE NBSMeasurementServices: Neutron... Open at page → 51 Page 51 PUBLICATIONS INTHESP250SERIESFROMTHECENTERFORRADIATIONRESEARCH SP250-1 NBSMeasurement Services: SP250-12 SpectralRadianceCalibrations J.H.Walker,R.D.Saunders, andA.T.Hattenburg SP250-2 NBSMeasurement Services: SP250-13 F... Open at page → 52 Page 52 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →