1、ANSI N42.25-1997(R2004) National Committee on Radiation Instrumentation, N42 accredited by the American National Standards Institute Secretariat The Institute of Electrical and Electronics Engineers, Inc. Reaffirmed 2 December 2004 Approved 6 January 1997 American National Standard Calibration andUs
2、age of Alpha/Beta Proportional Counters Sponsor American National Standards Institute Abstract: This standard establishes methods for the calibration and use of gas proportional counters with and without active guard detectors. This standard also establishes methods for mea-suring the alpha and beta
3、 counting plateau, crosstalk factors, background, alpha and betaefficiency from prepared standards, correction factors for samples whose self-attenuation or mass differs from that of the standard, and calculation of the sample activities together with their randomand total uncertainties. Correction
4、for pulse pileup due to high count rate is also discussed. Although many principles articulated in this standard apply to the counting of radionuclides emittinga maximum beta energy below 100 keV as well, the counting of these low-energy beta emitters requires a higher degree of attention to detail
5、in sample preparation, instrument calibration, and measurement correction factors than addressed in this standard. Therefore, this standard isintended for measuring radionuclides with maximum beta energies above 100 keV. Keywords: alpha/beta proportional counters, calibration The Institute of Electr
6、ical and Electronics Engineers, Inc. 345 East 47th Street, New York, NY 10017-2394, USA Copyright 1997 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 1997. Printed in the United States of America. ISBN 1-55937-903-0 No part of this publication may be re
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19、scope of those patents that are brought to its attention.iiiIntroduction(This introduction is not part of ANSI N42.25-1997, American National Standard Calibration and Usage of Alpha/BetaProportional Counters.)This standard is the responsibility of the Accredited Standards Committee on Radiation Inst
20、rumentation,N42. Committee N42 delegated development of this standard to Subcommittee N42.RM. Drafts werereviewed by Committee N42, Subcommittee N42.RM, and other interested parties, and the commentsreceived were utilized in producing the standard as finally approved. The standard was approved by N4
21、2letter ballot of 18 March 1996.At the time it approved this standard, the Accredited Standards Committee on Radiation Instrumentation,N42, had the following members:Louis Costrell, Chair Luigi Napoli, Administrative SecretaryOrganization Represented Name of RepresentativeAmerican Conference of Gove
22、rnmental Industrial HygienistsJesse LiebermanBattelle Pacific Northwest Laboratories Kenneth L. SwinthHealth Physics Society.George CampbellJoseph R. Stencel (Alt.)Institute of Electrical and Electronics Engineers.Louis CostrellJulian Forster (Alt.)Anthony J. Spurgin (Alt.)Lawrence Berkeley Laborato
23、ryEdward J. LampoLawrence Livermore National Laboratory.Paul L. PhelpsMassachusetts Institute of Technology, Bates Linear Accelerator Center .Frank X. MasseUS Army Center for EW/RSDA Edward GroeberUS Department of Commerce, National Institute of Standards and Technology Louis CostrellMichael Unterwe
24、ger (Alt.)US Department of EnergyGerald GoldsteinUS Federal Emergency Management Agency .Carl R. SiebentrittMembers-at-LargeJoseph C. BellianErnesto A. CorteJohn M. GallagherJack M. SelbyAl N. TschaecheEdward J. VallarioLee J. WagnerSanford WagnerAt the time this standard was approved, Subcommittee
25、N42.RM had the following members: Frank X. Masse, Chair J. M. R. Hutchinson, SecretaryRobert AyresJoseph G. BellianJohn D. BuchananR. F. ColeyBert M. CourseyMichael DevineRoger FerrisRobert J. GehrkeY. KobyashiMarkku KoskeloJ. L. LazewatskyDavid E. McCurdyD. M. MontgomeryCarl W. SeidelJohn SonewaldM
26、. P. UnterwegerivThe working group for this standard had the following members:Robert Gehrke, Project Leader Markku Koskelo, Project LeaderThe following persons were on the balloting committee that approved this document for submission to theAmerican National Standards Institute:Rochelle L. SternIEE
27、E Standards Project EditorDavid BaileyKenneth BloomfieldMichael DevineRick TomblinsonJoseph G. BellianHugh R. BrashearGeorge CampbellErnesto A. CorteLouis CostrellMorgan CoxJulian ForsterJohn M. GallagherGerald GoldsteinEdward GroeberEdward J. LampoJesse LiebermanFrank X. MassePaul L. PhelpsJack M.
28、SelbyCarl L. SiebentrittAnthony J. SpurginJoseph R. StencelKenneth L. SwinthAl N. TschaecheMichael UnterwegerEdward J. VallarioLee J. WagnerSanford WagnerEdward C. Wenzinger, Sr.vContents1. Overview 11.1 Scope 11.2 Special word usage 22. References 23. Definitions 23.1 Glossary . 23.2 Symbols . 53.3
29、 Apparatus . 54. Calibration 54.1 General. 54.2 Detector plateau measurement. 64.3 Discriminator settings 84.4 Background 94.5 Efficiency. 105. Sources. 115.1 Efficiency calibration sources 115.2 Check sources 116. Performance tests. 126.1 Sources. 126.2 Verification of counter background.126.3 Veri
30、fication of alpha, beta, and guard plateau bias points. 136.4 Verification of crosstalk (spillup/spilldown) . 136.5 Effectiveness of guard detector 136.6 Verification of alpha and beta efficiency. 146.7 Estimated uncertainty for gross alpha/beta screening 147. Determination of uncertainties and thei
31、r propagation . 158. Quality control and assurance 17Annex A (informative) Preparation of working standards from standard solutions . 19A.1 Simple volumetric preparation of planchet style sources 19A.2 Simple gravimetric preparation of planchet style sources . 20Annex B (informative) Guidance on mea
32、surement of samples 21B.1 General precautions . 21B.2 Net count rates . 21viB.3 Concentrations . 23B.4 Weight correction. 24B.5 Health physics smear samples . 25Annex C (informative) Bibliography 261American National Standard Calibration and Usage of Alpha/Beta Proportional Counters1. OverviewThis s
33、tandard provides a basis for the routine calibration and use of gas proportional counters with orwithout active guard detectors. Gas proportional counters are used for the measurement of alpha and betaemission rates, and for the measurement of radionuclide activities when interferences from otherrad
34、ionuclides are not present. This standard is intended for use by persons who have an understanding of theprinciples of gas proportional counting and are responsible for the development of correct procedures for thecalibration and use of these radiation measurement counters. References B6, B7, and B1
35、11provideinformation on the principles of operation of alpha/beta proportional counters.A typical alpha/beta gas proportional counter consists of one or more gas proportional counters, active guarddetectors, associated counting gas, signal processing electronics, and a scaler, or a multi-channel ana
36、lyzer torecord the detected counts. Computers are commonly interfaced to these systems to provide computercontrol as well as to permit automatic correction for efficiency, self attenuation, and other sample specificfactors, and for storage of quality assurance/quality control information. Automatic
37、propagation ofuncertainties is also provided by many commercially supplied computer-controlled instruments.1.1 ScopeThis standard establishes methods for the calibration and use of gas proportional counters with and withoutactive guard detectors. This standard also establishes methods for measuring
38、the alpha and beta countingplateau, crosstalk factors, background, alpha and beta efficiency from prepared standards, correction factorsfor samples whose self-attenuation or mass differs from that of the standard, and calculation of the sampleactivities together with their random and total uncertain
39、ties. Correction for pulse pileup due to high countrate is also discussed. Although many principles articulated in this standard apply to the counting ofradionuclides emitting a maximum beta energy below 100 keV as well, the counting of these low-energybeta emitters requires a higher degree of atten
40、tion to detail in sample preparation, instrument calibration, andmeasurement correction factors than addressed in this standard. Therefore, this standard is intended formeasuring radionuclides with maximum beta energies above 100 keV.1The numbers in brackets correspond to those of the bibliography i
41、n Annex C.ANSIN42.25-1997 AMERICAN NATIONAL STANDARD CALIBRATION AND USAGE OF21.2 Special word usageThe word shall denotes a requirement, the word should denotes a recommendation, and the word maydenotes permission. To conform to this standard, gas proportional counting shall be performed in accorda
42、ncewith the requirements of this standard, but not necessarily with its recommendations. However, justificationshould be documented for deviations from a recommendation.2. ReferencesANSI N42.14-1991, American National Standard Calibration and Use of Germanium Spectrometers for theMeasurement of Gamm
43、a-Ray Emission Rates of Radionuclides.2ANSI N42.22-1995, American National Standard Traceability of Radioactive Sources to the NationalInstitute of Standards and Technology (NIST) and Associated Instrument Quality Control.ANSI N42.23-1996, American National Standard Measurement and Associated Instru
44、mentation QualityAssurance for Radioassay Laboratories.3. Definitions3.1 Glossary3.1.1 active guard detector: A detector constructed from similar materials with similar geometry to themain sample counting detector. This detector is mounted in proximity to the sample counting detector inorder to inte
45、rcept and react to the same background cosmic and terrestrial radiation field as the sampledetector. Normally this detector is used in an anti-coincidence mode to cancel out the effect of thisbackground radiation field on the sample detector in order to produce a real-time adjusted net count rate fo
46、rthe sample detector.3.1.2 activity: The expected number of spontaneous nuclear decays (transformations) in unit time from aspecified energy state (excluding prompt decays from a lower nuclear level) for a given amount of aradionuclide. Its standard unit (SI) is the becquerel (Bq), where one Bq equa
47、ls one decay per second.Activity is often also expressed in curies, where 3.71010Bq equals one Ci exactly or in disintegrations perminute (dpm), where 1 dpm equals 1/60 Bq exactly.3.1.3 alpha emission rate: The rate at which alpha particles of all energies are emitted from one or allalpha-emitting r
48、adionuclides present in a source or sample.3.1.4 alpha surface emission rate: The rate at which alpha particles of all energies emanate from thesurface of a source or sample that contains one or more alpha-emitting radionuclides.3.1.5 attenuation: The net loss of radiation field from the sample resu
49、lting from scattering or absorption inthe sample or in material between the sample and the active volume of the counting chamber.3.1.6 background count rate: Events per unit time from radioactive decay not caused by a calibrationsource or sample but rather from that occurring in the surrounding environment or from cosmic-rayinteractions in or adjacent to the detector that have escaped detection by the guard detector, when present.2These ANSI N42 publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331,Piscataway, NJ 08855-
