1、Designation: E181 10E181 17Standard Test Methods forDetector Calibration and Analysis of Radionuclides1This standard is issued under the fixed designation E181; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover general procedures for the calibration of radiation detectors and the analysis of radionuclides. Foreac
3、h individual radionuclide, one or more of these methods may apply.1.2 These test methods are concerned only with specific radionuclide measurements. The chemical and physical properties ofthe radionuclides are not within the scope of this standard.1.3 The measurement standards appear in the followin
4、g order:SectionsSpectroscopy Methods:Calibration and Usage of Germa-nium Detectors 3 12Calibration and Usage of ScintillationDetector Systems: 13 20Calibration and Usage of ScintillationDetectors for Simple Spectra 16Calibration and Usage of ScintillationDetectors for Complex Spectra 17Counting Meth
5、ods:Beta Particle Counting 25-26Aluminum Absorption Curve 27 31Alpha Particle Counting 32 39Liquid Scintillation Counting 40 481.4 Additional information on the set-up, calibration and quality control for radiometric detectors and measurements is givenin Guide C1402 and Practice D7282.1.5 The values
6、 stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate saf
7、ety and health practices and determine the applicability of regulatorylimitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Stand
8、ards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Document2.1 ASTM Standards:2C1402 Guide for High-Resolution Gamma-Ray Spectrometry of Soil SamplesD7282 Practice for Set-up, Calibration, and Quality Control of Instrument
9、s Used for Radioactivity MeasurementsD7283 Test Method for Alpha and Beta Activity in Water By Liquid Scintillation CountingE170 Terminology Relating to Radiation Measurements and DosimetrySPECTROSCOPY METHODS1 These test methods are under the jurisdiction of ASTM Committee E10 on Nuclear Technology
10、 and Applications.Current edition approved Jan. 1, 2010June 1, 2017. Published February 2010June 2017. Originally approved in 1961. Last previous edition approved in 20032010 asE181 98E181 10.(2003). DOI: 10.1520/E0181-10.10.1520/E0181-17.2 For referencedASTM standards, visit theASTM website, www.as
11、tm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what c
12、hanges have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the of
13、ficial document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 certified radioactivity standard sourcea calibrated radioactive source, with stated accuracy, whose calibration is certifiedby the sou
14、rce supplier as traceable to the National Radioactivity Measurements System (1).33.1.2 check sourcea radioactivity source, not necessarily calibrated, that is used to confirm the continuing satisfactoryoperation of an instrument.3.1.3 FWHM(full width at half maximum) the full width of a gamma-ray pe
15、ak distribution measured at half the maximumordinate above the continuum.3.1.4 national radioactivity standard sourcea calibrated radioactive source prepared and distributed as a standard referencematerial by the U.S. National Institute of Standards and Technology.3.1.5 resolution, gamma raythe meas
16、ured FWHM, after background subtraction, of a gamma-ray peak distribution, expressedin units of energy.3.2 Abbreviations:3.2.1 MCAMultichannel Analyzer.3.2.2 SCASingle Channel Analyzer.3.2.3 ROIRegion-Of-Interest.3.3 For other relevant terms, see Terminology E170.3.4 correlated photon summingthe sim
17、ultaneous detection of two or more photons originating from a single nucleardisintegration.3.5 dead timethe time after a triggering pulse during which the system is unable to retrigger.NOTE 1The terms “standard source” and “radioactivity standard” are general terms used to refer to the sources and s
18、tandards of NationalRadioactivity Standard Source and Certified Radioactivity Standard Source.CALIBRATION AND USAGE OF GERMANIUM DETECTORS4. Scope4.1 This standard establishes methods for calibration, usage, and performance testing of germanium detectors for themeasurement of gamma-ray emission rate
19、s of radionuclides. It covers the energy and full-energy peak efficiency calibration as wellas the determination of gamma-ray energies in the 0.06 to 2-MeV energy region and is designed to yield gamma-ray emission rateswith an uncertainty of 63 % (see Note 2). This method applies primarily to measur
20、ements that do not involve overlapping peaks,and in which peak-to-continuum considerations are not important.NOTE 2Uncertainty U is given at the 68 % confidence level; that is, U5=(i211/3(i2 where i are the estimated maximum systematicuncertainties, and i are the random uncertainties at the 68 % con
21、fidence level (2). Other methods of error analysis are in use (3, 4).4. Scope4.1 This standard establishes methods for calibration, usage, and performance testing of germanium detectors for themeasurement of gamma-ray emission rates of radionuclides. It covers the energy and full-energy peak efficie
22、ncy calibration as wellas the determination of gamma-ray energies in the 0.06 to 2-MeV energy region and is designed to yield gamma-ray emission rateswith an uncertainty of 63 % (see Note 2). This method applies primarily to measurements that do not involve overlapping peaks,and in which peak-to-con
23、tinuum considerations are not important.NOTE 2Uncertainty U is given at the 68 % confidence level; that is, U5=(i211/3(i2 where i are the estimated maximum systematicuncertainties, and i are the random uncertainties at the 68 % confidence level (2). Other methods of error analysis are in use (3, 4).
24、5. Apparatus5.1 A typical gamma-ray spectrometry system consists of a germanium detector (with its liquid nitrogen cryostat, preamplifier,and possibly a high-voltage filter) in conjunction with a detector bias supply, linear amplifier, multichannel analyzer, and datareadout device, for example, a pr
25、inter, plotter, oscilloscope, or computer. Gamma rays interact with the detector to produce pulseswhich are analyzed and counted by the supportive electronics system.6. Summary of Methods6.1 The purpose of these methods is to provide a standardized basis for the calibration and usage of germanium de
26、tectors formeasurement of gamma-ray emission rates of radionuclides. The method is intended for use by knowledgeable persons who areresponsible for the development of correct procedures for the calibration and usage of germanium detectors.3 The boldface numbers in parentheses refer to the list of re
27、ferences at the end of these methods.E181 1726.2 A source emission rate for a gamma ray of a selected energy is determined from the counting rate in a full-energy peak ofa spectrum, together with the measured efficiency of the spectrometry system for that energy and source location. It is usually no
28、tpossible to measure the efficiency directly with emission-rate standards at all desired energies. Therefore a curve or function isconstructed to permit interpolation between available calibration points.7. Preparation of Apparatus7.1 Follow the manufacturers instructions for setting up and prelimin
29、ary testing of the equipment. Observe all of themanufacturers limitations and cautions.All tests described in Section 12 should be performed before starting the calibrations, andall corrections shall be made when required.Acheck source should be used to check the stability of the system at least bef
30、ore andafter the calibration.8. Calibration Procedure8.1 Energy CalibrationDetermine the energy calibration (channel number versus gamma-ray energy) of the detector systemat a fixed gain by determining the channel numbers corresponding to full energy peak centroids from gamma rays emitted overthe fu
31、ll energy range of interest from multipeaked or multinuclide radioactivity sources, or both. Determine nonlinearity correctionfactors as necessary (5).8.1.1 Using suitable gamma-ray compilations (6-14), plot or fit to an appropriate mathematical function the values for peakcentroid (in channels) ver
32、sus gamma energy.8.2 Effciency Calibration:8.2.1 Accumulate an energy spectrum using calibrated radioactivity standards at a desired and reproducible source-to-detectordistance. At least 20 000 net counts should be accumulated in each full-energy gamma-ray peak of interest using National orCertified
33、 Radioactivity Standard Sources, or both (see 12.1, 12.5, and 12.6).8.2.2 For each standard source, obtain the net count rate (total count rate of region of interest minus the Compton continuumcount rate and, if applicable, the ambient background count rate within the same region) in the full-energy
34、 gamma-ray peak, orpeaks, using a tested method that provides consistent results (see 12.2, 12.3, and 12.4).8.2.3 Correct the standard source emission rate for decay to the count time of 8.2.2.8.2.4 Calculate the full-energy peak efficiency, Ef, as follows:Ef 5NpN(1)where:Ef = full-energy peak effic
35、iency (counts per gamma ray emitted),Np = net gamma-ray count in the full-energy peak (counts per second live time) (Note 3) (see 8.2.2), andN = gamma-ray emission rate (gamma rays per second).NOTE 3Any other unit of time is acceptable provided it is used consistently throughout.8.2.5 There are many
36、 ways of calculating the net gamma-ray count. The method presented here is a valid, common methodwhen there are no interferences from photopeaks adjacent to the peak of interest, and when the continuum varies linearly from oneside of the peak to the other.8.2.5.1 Other net peak area calculation meth
37、ods can also be used for single peaks, and must be used when there is interferencefrom adjacent peaks, or when the continuum does not behave linearly. Other methods are acceptable, if they are used in a consistentmanner and have been verified to provide accurate results.8.2.5.2 Using a simple model,
38、 the net peak area for a single peak can be calculated as follows:NA 5Gs 2B 2I (2)where:Gs = gross count in the peak region-of-interest (ROI) in the sample spectrum,B = continuum, andI = number of counts in the background peak (if there is no background peak, or if a background subtraction is not pe
39、rformed,I = 0).8.2.5.3 The net gamma-ray count, Np is related to the net peak area as follows:Np 5NATs(3)where Ts = spectrum live time.8.2.5.4 The continuum, B, is calculated from the sample spectrum using the following equation (see Fig. 1):B 5 N2n B1s1B2s! (4)E181 173where:N = number of channels i
40、n the peak ROI,n = number of continuum channels on each side,4B1s = sum of counts in the low-energy continuum region in the sample spectrum, andB2 s = sum of counts in the high-energy continuum region in the sample spectrum.NOTE 4These equations assume that the channels that are used to calculate th
41、e continuum do not overlap with the peak ROI, and are adjacent to it,or have the same size gap between the two regions on both sides. A different equation must be used, if the gaps are of a different size.The peaked background, I, is calculated from a separate background measurement using the follow
42、ing equation:I 5 TsTbIb (5)where:Ts = live time of the sample spectrum,Tb = live time of the background spectrum, andIb = net background peak area in the background spectrum.If a separate background measurement exists, the net background peak area is calculated from the following equation:Ib 5Gb 2Bb
43、 (6)where:Gb = sum of gross counts in the background peak region (of the background spectrum), andBb = continuum counts in the background peak region (of the background spectrum).The continuum counts in the background spectrum are calculated from the following equation:Bb 5 N2n B1b1B2b! (7)where:N =
44、 number of channels in the background peak ROI,n = number of continuum channels on each side (assumed to be the same on both sides),B1b = sum of counts in the low-energy continuum region in the background spectrum, andB2b = sum of counts in the high-energy continuum region in the background spectrum
45、.8.2.5.5 If the standard source is calibrated in units of Becquerels, the gamma-ray emission rate is given by:N5AP (8)4 For simplicity of these calculations, n is assumed to be the same on both sides of the peak. If the continuum is calculated using a different number of channels on theleft of the p
46、eak than on the right of the peak, different equations must be used.FIG. 1 Typical Spectral Peak With Parameters Used in the Peak Area Determination IndicatedE181 174where:A = number of nuclear decays per second, andP = probability per nuclear decay for the gamma ray (7-14).8.2.6 Plot, or fit to an
47、appropriate mathematical function, the values for full-energy peak efficiency (determined in 8.2.4) versusgamma-ray energy (see 12.5) (15-23).9. Measurement of Gamma-Ray Emission Rate of the Sample9.1 Place the sample to be measured at the source-to-detector distance used for efficiency calibration
48、(see 12.6).9.1.1 Accumulate the gamma-ray spectrum, recording the count duration.9.1.2 Determine the energy of the gamma rays present by use of the energy calibration obtained under, and at the same gainas 8.1.9.1.3 Obtain the net count rate in each full-energy gamma-ray peak of interest as describe
49、d in 8.2.2.9.1.4 Determine the full-energy peak efficiency for each energy of interest from the curve or function obtained in 8.2.5.9.1.5 Calculate the number of gamma rays emitted per unit live time for each full-energy peak as follows:N5NpEf(9)When calculating a nuclear transmutation rate from a gamma-ray emission rate determined for a specific radionuclide, aknowledge of the gamma-ray probability per decay is required (7-14), that is,A 5NP(10)9.1.6 Calculate the net peak area uncertainty as follows:SNA 5Gs1SN2nD2B1s1B2s!1ST
