1、ANSI N42.28-2002IEEE StandardsN42.28American National Standard forCalibration of Germanium Detectorsfor In-Situ Gamma-Ray MeasurementsPublished by The Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY10016-5997, USA26 February 2004Accredited by the American National
2、Standards InstituteSponsored by theNational Committee on Radiation Instrumentation, N42IEEE StandardsPrint: SH95154PDF: SS95154The Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 10016-5997, USACopyright 2003 by the Institute of Electrical and Electronic Engineers,
3、 Inc.All rights reserved. Published 26 February 2004. Printed in the United States of America.Print: ISBN 0-7381-3763-4 SH95154PDF: ISBN 0-7381-3764-2 SS95154No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permissio
4、n from the publisher.ANSI N42.28-2002American National Standard for Calibration of Germanium Detectors for In-Situ Gamma-Ray MeasurementsSponsorNational Committee on Radiation Instrumentation, N42Accredited by the American National Standards InstituteSecretariatThe Institute of Electrical and Electr
5、onics Engineers, Inc.Approved 6 September 2002American National Standards InstituteAbstract: The need for accurately measuring radioactivity in-situ for a variety of detector charac-terization techniques requires that performance criteria for efficiency calibration be developed, andsuch a calibratio
6、n technique is described in this standard. Keywords: calibration, gamma-ray, germanium detectors, in-situAmerican National StandardAn American National Standard implies a consensus of those substantially concerned with its scope and pro-visions. An American National Standard is intended as a guide t
7、o aid the manufacturer, the consumer, andthe general public. The existence of an American National Standard does not in any respect preclude any-one, whether he has approved the standard or not, from manufacturing, marketing, purchasing, or usingproducts, processes, or procedures not conforming to t
8、he standard. American National Standards are subjectto periodic reviews and users are cautioned to obtain the latest editions.CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The pro-cedures of the American National Standards Institute require that action be t
9、aken to affirm, revise, or with-draw this standard no later than five years from the date of publication. Purchasers of American NationalStandards may receive current information on all standards by calling or writing the American NationalStandards Institute.Authorization to photocopy portions of an
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11、222 Rosewood Drive, Danvers, MA 01923 USA; +1-978-750-8400. Permission to photo-copy portions of any individual standard for educational classroom use can also be obtained through theCopyright Clearance Center.Copyright 2004 IEEE. All rights reserved. iiiIntroduction(This introduction is not part of
12、 ANSI N42.28-2002, American National Standard for Calibration of Germanium Detec-tors for In-Situ Gamma-Ray Measurements.)This standard is the responsibility of the Accredited American Standards Committee on Radiation Instru-mentation, N42. Committee N42 delegated the development of this standard to
13、 Subcommittee N42.RM.Drafts were reviewed by Committee N42, Subcommittee N42.RM, and other interested parties; and thecomments were utilized in producing the standard as finally approved. This standard was approved on N42letter ballot of 25 September 2002. ParticipantsAt the time Committee N42 appro
14、ved this standard, it had the following members:Louis Costrell, ChairMichael P. Unterweger, Vice ChairSue Vogel, Administrative SecretaryOrganization Represented Name of RepresentativeAmerican Conference of Governmental Industrial HygienistsJesse LiebermanBattelle Pacific Northwest Laboratories Jose
15、ph C. McDonaldConsultant Morgan CoxEberline Instruments Mitchell TruittEntergy-ANO.Ron SchwartzHealth Physics Society.Joseph R. StencelInstitute of Electrical and Electronics Engineers, IncLouis CostrellJulian Forster (Alt.)Anthony J. Spurgin (Alt.)Lawrence Berkeley Laboratory . Edward J. LampoLawre
16、nce Livermore Laboratory . Gary JohnsonMassachusetts Institute of Technology, Bates Linear Accelerator Center, RPO . Frank X. MasseOak Ridge National Laboratory.Charles L. BrittonPeter J. Chiaro, Jr. (Alt.)ORTEC.Ronald M. KeyserOverhoff Technology Corporation.Mario W. OverhoffSaint-Gobain Richard P.
17、 OxfordSwinth Associates Kenneth L. SwinthThermo Gamma-MetricsErnesto A. CorteU.S. National Institute of Standards referto ANSI N42.14-1999 and IEC 61275-1997-09 for such methods.CAUTIONWhile guidance on the application of in-situ gamma-ray spectrometry and the use of in-situ measurementdata is beyo
18、nd the scope of this standard, some general remarks concerning the technique are warranted. As with anymeasurement technique, one must be aware of assumptions that give rise to limitations on the range of potential applica-tions. In-situ measurements carry specific assumption regarding many measurem
19、ent parameters. The most notableparameter is the distribution of activity in the source. A detector measures only the gamma-ray fluence from which onecan infer an activity concentration. The extent to which the measurement assumptions reflect the actual or true measure-ment conditions is the extent
20、to which the measurements results will satisfy their intended purpose. For example, adetector that is calibrated to measure sources with uniformly distributed activity will produce inconsistent and mislead-ing results if the source is highly heterogeneous. However, there could be an acceptable degre
21、e of heterogeneity thatwould still allow for useful data. Service providers and their customers should consider using data quality objectives as aguide or a means to evaluate a measurement program that uses or intends to use this technique.2. ReferencesThis standard shall be used in conjunction with
22、 the following publications. When the followingspecifications are superseded by an approved revision, the revision shall apply.ANSI/ASQC E4-1994, American National Standard Specifications and Guidelines for Quality Systems forEnvironmental Data Collection and Environmental Technology Programs.1ANSI
23、N42.23-1996, American National Standard Measurement and Associated Instrumentation QualityAssurance for Radioassay Laboratories.ANSI N42.14-1999, American National Standard for Calibration and Use of Germanium Spectrometers forthe Measurement of Gamma-Ray Emission Rates of Radionuclides.HPS N13.30-1
24、996, Performance Criteria for Radiobioassay.2IEC 61275-1997-09, Radiation protection instrumentationMeasurement of discrete radionuclides in theenvironmentIn-situ photon spectrometry system using a germanium detector.33. DefinitionsThe word “shall” denotes a requirement, the word “should” denotes a
25、recommendation, and the word “may”denotes permission. To conform to this standard, in-situ gamma-ray spectrometry measurements (hereafterreferred to as in-situ measurements) shall be evaluated according to the requirements of this standard, butnot necessarily with its recommendations; however, justi
26、fication should be documented for deviations froma recommendation.1ANSI publications are available from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor,New York, NY 10036, USA (http:/www.ansi.org/).2HPS standards are available from HPS, 1313 Dolley Madison
27、 Blvd., Suite 402, MacLean, VA 22101, USA, Fax 703-790-2672 (http:/hps.org/documents/).3IEC publications are available from the Sales Department of the International Electrotechnical Commission, Case Postale 131, 3, ruede Varemb, CH-1211, Genve 20, Switzerland/Suisse (http:/www.iec.ch/). IEC publica
28、tions are also available in the United Statesfrom the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, USA.GERMANIUM DETECTORS FOR IN-SITU GAMMA-RAY MEASUREMENTS ANSI N42.28-2002Copyright 2004 IEEE. All rights reserved. 3For the purposes of
29、 this standard, the following terms and definitions apply:3.1 absorber: Any material that absorbs or diminishes the gamma-ray fluence from the source.3.2 activity concentration: The expected number of spontaneous nuclear decays (transformations) pergram, per surface or volume of material in a unit t
30、ime from a specified energy state (excluding promptdecays from a lower nuclear level) for a given amount of a radionuclide. Its standard unit (SI) is the bec-querel (Bq) per mass, volume or surface area, where one Bq equals one decay per second. Activity concen-tration has often been expressed in cu
31、ries (Ci), where 3.7 1010Bq equals 1 Ci, exactly.NOTEThe activity concentration is generally abbreviated to concentration and is sometimes called the specificactivity.3.3 attenuated source: A source is attenuated when at least 25% of the gamma rays emitted from the sourceand in the direction of the
32、detector arrive at the detector having undergone some energy reduction as a resultof interactions with absorbers between the source and the detectors encap.NOTEThe absorbers are generally part of the source, such as a container. 3.4 calibration: The determination of a value that converts a measured
33、number into a desired physical quan-tity (e.g., pulse height into photon energy, or counts per second into an activity concentration).NOTEThe calibration refers to a process, procedure, and/or methodology by which one determines an efficiencyvalue.3.5 coefficient of variation (CV): The standard devi
34、ation divided by the average value.3.6 collimated: Refers to the use of absorbers with transmission holes between the source and the detectorto reduce or restrict the detectors field of view.3.7 combined standard uncertainty (uc): The uncertainty resulting from combining category A and cate-gory B u
35、ncertainties, as defined by the Bureau International des Poids et Measures (BIPM), using standardstatistical methods. Category A uncertainties are evaluated by applying statistical methods to a series ofrepeated measurements and are characterized by the estimated standard deviation, A; category B un
36、certain-ties are assigned to quantities whose variation is not explicitly observed. Category B uncertainties are deter-mined by estimating from other information an approximation to a corresponding “standard deviation,” B,whose existence is assumed. They are combined as if they are all standard devi
37、ations.3.8 containerized source: A radioactive source that is encased or sealed in a specific, regularly shapedcontainer.3.9 conventional true value: The value attributed to a particular quantity and accepted, sometimes by con-vention, as having an uncertainty appropriate for a given purpose. Syn: r
38、eference value. 3.10 counting rate: The rate at which detector pulses are being registered in a selected voltage interval. Theunits are s1.3.11 customer: The recipient and user of the in-situ measurement data.3.12 efficiency: The ratio between the detector response, e.g., the number of selected puls
39、es recorded perunit time to the number of gamma rays emitted by the source per unit time.NOTEThe efficiency as it is defined above corresponds to what usually is referred to as the absolute efficiency.3.13 field conditions: Environmental and operating conditions under which an in-situ measurement is
40、performed.ANSI N42.28-2002 AMERICAN NATIONAL STANDARD FOR CALIBRATION OF4 Copyright 2004 IEEE. All rights reserved.3.14 field of view (FOV): The portion of the source that is bounded by the solid angle subtended by thedetector (with respect to the source) in which 90% of photons that are recorded in
41、 the full energy photopeakor photopeaks of the spectrum for the energy or energies of interest.NOTEThe FOV varies with gamma-ray energy, source thickness, composition and density of the source, externalattenuation, as well as properties of the detector. The FOV can be expressed in terms of the solid
42、 angle or in terms of thelinear dimensions of the source.3.15 full-energy peak: A peak in the spectrum resulting from the complete (total) absorption of gamma raysof a given energy in the active volume of the detector and the collection of all of the resulting charge. Syn:photopeak.3.16 high energy:
43、 High energy refers to a range of gamma-ray energies. If E is the gamma-ray energy, thena photon is high energy if 100 63% of the photons have undergone energy reductionSource size Large: source occupies 80% of the detectors FOVSmall: source occupies five times the MFP for the gamma-ray energy teste
44、dThin: factor of five reduction in the signal (e.g., counts or count rate)GERMANIUM DETECTORS FOR IN-SITU GAMMA-RAY MEASUREMENTS ANSI N42.28-2002Copyright 2004 IEEE. All rights reserved. 96.1 Partial compliance and limitations on test resultsIf the service provider is performing a limited range of m
45、easurements for a specific application, then at leastthose configurations that are appropriate for the application in question shall be performance tested. In thiscase, the service provider will be in, and shall only claim, partial compliance with this standard, assumingthat the service provider mee
46、ts the criteria set forth in Clause 7.The results of the performance tests are valid indefinitely, unless the measurement conditions, instrumentparameters, or aspects of the calibration are modified to the extent that the efficiency is or could be affected. 7. Characterizing the performance7.1 Perfo
47、rmance specificationThe performance for a given test shall be passed if the relative bias of the measured value summed with therelative standard uncertainty for the reference value (yt) and the relative standard uncertainty for themeasured value (ym), is less than or equal to the tolerance level, L,
48、 for the test configuration. That is, if(1)The measured value can be the activity, activity concentration, emission rate density, or efficiency.The relative bias, B, is given byB = (ym yt)/ytand the relative combined uncertainty uc,r(yt) of the source isuc,r(yt) = uc(yt)/ytSimilarly, the relative co
49、mbined uncertainty uc,r(ym) of the measurement is given byuc,r(ym) = uc(ym)/ymThe relative bias is an indication of the degree to which the calibration will produce detector efficiencies thatyield accurate results. The relative standard uncertainty of the reference value is a measure of the precisionof the source. Similarly, the relative standard uncertainty of the measured value is an indication of theprecision of the measurement value. See Clause 8 for guidance on the evaluation of the combined standarduncertainty associated with the measurement. Table 2 lists
