1、The Institute of Electrical and Electronics Engineers, Inc.345 East 47th Street, New York, NY 10017-2394, USACopyright 1995 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 1995. Printed in the United States of America.ISBN 1-55937-491-8No part of this pub
2、lication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.ANSI N42.12-1994(R2004)(Revision of ANSI N42.12-1980)American National Standard Calibration and Usage of Thallium-Activated Sodium Iodide Detector Systems for
3、 Assay of RadionuclidesSponsorNational Committee on Radiation Instrumentation, N42accredited by theAmerican National Standards InstituteSecretariatThe Institute of Electrical and Electrical Engineers, Inc.Reaffirmed December 2, 2004American National Standards InstituteAbstract: Methods for performan
4、ce testing, calibration, and usage of NaI(Tl) detector systems forthe measurement of gamma ray emission rates of radionuclides; the assay for radioactivity; and thedetermination of gamma ray energies and intensities are established. Both energy calibration andefficiency calibration are covered.Keywo
5、rds: calibration, efficiency calibration, energy calibration, gamma-ray energy, radioactivity,radionuclidesIEEE Standards documents are developed within the Technical Committees of theIEEE Societies and the Standards Coordinating Committees of the IEEE StandardsBoard. Members of the committees serve
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13、eived formal consideration. Comments on standards and requests for interpretations should be addressed to:Secretary, IEEE Standards Board445 Hoes LaneP.O. Box 1331Piscataway, NJ 08855-1331USAIEEE Standards documents may involve the use of patented technology. Theirapproval by the Institute of Electr
14、ical and Electronics Engineers does not mean thatusing such technology for the purpose of conforming to such standards is authorizedby the patent owner. It is the obligation of the user of such technology to obtain allnecessary permissions.iiiIntroduction(This introduction is not a part of ANSI N42.
15、12-1994, American National Standard Calibration and Usage of Thallium-Activated Sodium Iodide Detector Systems for Assay of Radionuclides.)This standard, a revision of ANSI N42.12-1980, is the responsibility of the Accredited Standards CommitteeN42 on Radiation Instrumentation. Committee N42 delegat
16、ed the development of this standard to its Sub-committee N42.2. Drafts were reviewed by Committee N42, Subcommittee N42.RM on Radioactivity Mea-surements, and other interested parties, and the comments received were utilized in producing the standardas finally approved. The standard was approved by
17、N42 letter ballot of 11 April 1994.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 G
18、overnmental Industrial HygienistsJesse LiebermanHealth Physics Society.George CampbellJoseph R. Stencel (Alt.)Institute of Electrical and Electronics Engineers.Louis CostrellJulian Forster (Alt.)Anthony J. Spurgin (Alt.)Lawrence Berkeley LaboratoryEdward J. LampoLawrence Livermore National Laborator
19、y.Paul L. PhelpsNational Institute of Standards and TechnologyLouis CostrellMichael P. Unterweger (Alt.)Oak Ridge National Laboratory.Hugh R. BrashearPacific Northwest LaboratoriesKenneth L. SwinthUS Army Center for EW/RSTA.Edward GroeberUS Department of EnergyGerald GoldsteinUS Federal Emergency Ma
20、nagement Agency .Carl R. SiebentrittUS Nuclear Regulatory Commission.Edward C. Wenzinger, Sr.Members-at-LargeJoseph C. BellianErnesto A. CorteMorgan CoxJohn M. GallagherJack M. SelbyAl N. TschaecheEdward J. VallarioLee J. WagnerSanford Wagner At the time this standard was approved, Subcommittee N42.
21、RM had the following members: Frank X. Masse, Chair J. M. R. Hutchinson, SecretaryRobert Ayres Bert M. Coursey Y. KobyashiJoseph G. Bellian Michael Devine David McCurdyJohn D. Buchanan Roger Ferris D. M. MontgomeryR. F. Coley Robert J. Gehrke Carl W. SeidelivThe working group for this standard had t
22、he following members:Joseph G. Bellian, Project LeaderRod Dayton Tom Jenkins Robert KinzerJ. M. R. Hutchinson Peter Paul Ernesto A. CorteMelvyn Halbert Don W. Miller Frank X. Massey The following persons were on the balloting committee:Joseph G. Bellian Gerald Goldstein Anthony J. SpurginHugh R. Bra
23、shear Edward Groeber Joseph R. StencilGeorge Campbell Edward J. Lampo Kenneth L. SwinthErnesto A. Corte Jesse Lieberman Al N. TschaecheLouis Costrell Paul L. Phelps Michael UnterwegerMorgan Cox Jack M. Selby Edward J. VallarioJulian Forster Carl L. Siebentritt Sanford WagnerJohn M. Gallagher Edward
24、C. Wenzinger, Sr.Mary Lynne NielsenIEEE Standards Project EditorvContentsCLAUSE PAGE1. Overview 11.1 Scope 11.2 Purpose. 12. References 23. Definitions 24. Procedure . 34.1 Total spectrum counting systems. 34.2 SCA counting systems . 54.3 MCA counting systems 65. Sources of systematic error 86. Prec
25、autions. 96.1 Assay for a radionuclide for which no radioactivity standard is readily available 96.2 Assay of mixtures of radionuclides 96.3 Thin-Window detectors . 96.4 Count rates . 96.5 Geometric correction factors 96.6 Counting statistics 96.7 Dead-Time corrections. 96.8 Correction for decay dur
26、ing the counting period. 106.9 Counting geometry. 116.10 Spectral features. 116.11 Full-Energy-Peak efficiency versus energy function or curve 116.12 Net count rate. 126.13 Temperature effects . 126.14 Linearity. 127. Bibliography 121American National Standard Calibration and Usage of Thallium-Activ
27、ated Sodium Iodide Detector Systems for Assay of Radionuclides1. Overview1.1 ScopeThis standard establishes methods for performance testing, calibration, and usage of thallium-activatedsodium iodide NaI(Tl) detector systems for the measurement of gamma ray emission rates of radionu-clides; the assay
28、 for radioactivity; and the determination of gamma ray energies and intensities. It coversboth energy calibration and efficiency calibration. The following three techniques are considered:a) Total spectrum counting (see 4.1) employs a system that counts all pulses above a low-energythreshold (see 6.
29、1, 6.2, and 6.3).b) Single-channel analyzer (SCA) counting (see 4.2) employs a system with a counting “window,”which establishes upper and lower energy boundaries (see 6.1, 6.2, and 6.3).c) Multichannel analyzer (MCA) counting (see 4.3) employs a system in which multiple counting win-dows are utiliz
30、ed. This technique allows measurements for which the continuum under the full-energy peak may be subtracted without introducing unacceptable error.In case of overlapping peaks in the spectrum, it is realized that an MCA with access to a spectrum-strippingprogram is necessary. Such cases are not cove
31、red by this standard.1.2 PurposeThe purpose of this document is to provide a standardized basis for the calibration and usage of sodiumiodide detector systems for the measurement of gamma ray emission rates of radionuclides. Typical applica-tions include radionuclide identification and assay in vari
32、ous industrial, environmental, and medical applica-tions. An NaI(Tl) detector system consists of three major components: a scintillating medium that producesa flash of light when ionizing radiation interacts with it; one or more photomultipliers, optically coupled tothe scintillator, which converts
33、the light flash to an amplified electrical impulse; and associated electronicinstrumentation that powers the photomultiplier and processes the output signal. (See IEEE Std 398-1972.1)1Information on the reference can be found in clause 2.ANSIN42.12-1994 AMERICAN NATIONAL STANDARD CALIBRATION AND USA
34、GE OF THALLIUM-ACTIVATED2The theory of operation of NaI(Tl) detectors is presented in numerous publications, including B3, B5,and B9 in clause 7.2. ReferencesThis standard shall be used in conjunction with the following publication:IEEE Std 398-1972 (Reaff 1990), IEEE Standard Test Procedures for Ph
35、otomultipliers for ScintillationCounting and Glossary for Scintillation Counting Field (ANSI).23. Definitions3.1 accuracy: The degree of agreement of the measured value with the true value of the quantity beingmeasured.3.2 assay: The determination of the activity of a radionuclide in a sample.3.3 am
36、bient background: Those counts that can be observed, and thereby allowed for, by measuring a sam-ple that is identical to the unknown sample in all respects except for the absence of radioactivity. Thesecounts are attributable to environmental radioactivity in the detector itself, the detector shiel
37、ding material,and the sample container; cosmic rays; electronic noise pulses; etc.3.4 check source: A radioactive source, not necessarily calibrated, that is used to confirm the continuing sat-isfactory operation of an instrument.3.5 correlated gamma ray summing: The simultaneous detection of two or
38、 more gamma rays originatingfrom a single atom disintegration.3.6 dead time (td): The time after a triggering pulse during which the system is unable to retrigger.3.7 efficiency: The net number of counts registered by the detector system per unit of time, divided by thenumber of photons of interest
39、originating in the radioactive source during the same unit of time.3.8 energy calibration: The relationship between the height of the amplifier output pulse and the energy ofthe photons originating in the radioactive source.3.9 full-energy peak: The peak in a pulse height spectrum that corresponds t
40、o total absorption of a gammaphoton in the NaI(Tl) detector.3.10 full width at half maximum (FWHM): The full width of a gamma photon peak distribution measuredat an ordinate halfway between the maximum ordinate of the peak and the background.3.11 live time: The total time of the measurement minus th
41、e total dead time.3.12 precision: The degree of agreement of repeated measurements of the same property, expressed quanti-tatively as the standard deviation computed from the results of the series of measurements.3.13 pulse height radiation: See 3.16.2IEEE publications are available from the Institu
42、te of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway,NJ 08855-1331, USA.ANSISODIUM IODIDE DETECTOR SYSTEMS FOR ASSAY OF RADIONUCLIDES N42.12-199433.14 radioactivity standard source: A radioactivity standard, as used in this document, shall be either aradioactivity sta
43、ndard that has been certified as to absolute radioactivity by a laboratory recognized as theNational Standardizing Laboratory of a country for radioactivity measurements or a radioactivity standardthat has been obtained from a supplier who participates in measurement assurance activities with theNat
44、ional Standardizing Laboratory when such standards are available. In such measurement assurance activ-ities, the radioactivity calibration value of the suppliers should agree with the National Standardizing Labo-ratory value within the overall uncertainty stated by the supplier in its certification
45、of the same batch ofsources or in its certification of similar sources.3.15 random photon summing: The simultaneous detection of two or more photons originating from thedisintegrations of more than one atom.3.16 resolution, pulse height: The measured FWHM, after ambient background subtraction, of a
46、gamma-ray peak distribution, expressed as a percentage of the pulse height corresponding to the centroid of the dis-tribution.3.17 sensitivity response: The net number of counts registered by the detector system per unit of time,divided by the activity of the radionuclide.3.18 shall: A verb indicati
47、ng an action required by this standard.3.19 should: A verb indicating an action that is to be included when practical.3.20 simulated source: A radioactive source consisting of one or more long-lived radionuclides that arechosen to simulate the radiations from a short-lived or unavailable radionuclid
48、e of interest.3.21 window width: The difference between the upper-level and lower-level discriminator settings.4. Procedure4.1 Total spectrum counting systems4.1.1 GeneralAll instruments shall be installed and operated in accordance with the instructions of the manufacturer (seeclause 6). The activi
49、ty of a radionuclide can only be determined if the instrument has been calibrated with astandard source (or simulated standard source) of the radionuclide being assayed and in the absence of otherradionuclides.4.1.2 Sensitivity response calibrationa) Set the low-level discriminator to a value such that the following conditions are satisfied:1) The gamma rays of interest are being counted.2) The system response is as insensitive as possible to small changes in discriminator setting.3) Any electronic noise is below the counting threshold.b) For each radionuclide of interest, accumulat
