1、Designation: C1402 04 (Reapproved 2009)C1402 17Standard Guide forHigh-Resolution Gamma-Ray Spectrometry of Soil Samples1This standard is issued under the fixed designation C1402; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. 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 This guide covers the identification and quantitative determination of gamma-ray emitting radionuclides in soi
3、l samples bymeans of gamma-ray spectrometry. It is applicable to nuclides emitting gamma rays with an approximate energy range of 20 to2000 keV. For typical gamma-ray spectrometry systems and sample types, activity levels of about 5 Bq (135 pCi) are measuredeasily for most nuclides, and activity lev
4、els as low as 0.1 Bq (2.7 pCi) can be measured for many nuclides. It is not applicable toradionuclides that emit no gamma rays such as the pure beta-emitting radionuclides hydrogen-3, carbon-14, strontium-90, andbecquerel quantities of most transuranics. This guide does not address the in situ measu
5、rement techniques, where soil is analyzedin place without sampling. Guidance for in situ techniques can be found in Ref (1) and (2).2 This guide also does not discussmethods for determining lower limits of detection. Such discussions can be found in Refs (3),(4),(5), and (6).1.2 This guide can be us
6、ed for either quantitative or relative determinations. For quantitative assay, the results are expressed interms of absolute activities or activity concentrations of the radionuclides found to be present. This guide may also be used forqualitative identification of the gamma-ray emitting radionuclid
7、es in soil without attempting to quantify their activities. It can alsobe used to only determine their level of activities relative to each other but not in an absolute sense. General information onradioactivity and its measurement may be found in Refs (7),(8),(9),(10), and (11) and Standard Test Me
8、thods E181. Informationon specific applications of gamma-ray spectrometry is also available in Refs (12) or (13). Practice D3649 may be a valuable sourceof information.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 Th
9、is standard may involve hazardous material, operations, and equipment. This standard does not purport to address allof the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriatesafety and health practices and determine the app
10、licability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the
11、 World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C859 Terminology Relating to Nuclear MaterialsC998 Practice for Sampling Surface Soil for RadionuclidesC999 Practice for Soil Sample Preparation for the Determination of RadionuclidesC100
12、9 Guide for Establishing and Maintaining a Quality Assurance Program for Analytical Laboratories Within the NuclearIndustryD3649 Practice for High-Resolution Gamma-Ray Spectrometry of WaterD7282 Practice for Set-up, Calibration, and Quality Control of Instruments Used for Radioactivity MeasurementsE
13、181 Test Methods for Detector Calibration and Analysis of RadionuclidesIEEE/ASTM-SI-10 Standard for Use of the International System of Units (SI) the Modern Metric System1 This guide is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommitte
14、e C26.05 on Methods of Test.Current edition approved June 1, 2009June 1, 2017. Published July 2009July 2017. Originally approved in 1998. Last previous edition approved in 20042009 asC1402 04.C1402 04 (2009). DOI: 10.1520/C1402-04R09.10.1520/C1402-17.2 The boldface numbers in parentheses refer to th
15、e list of references at the end of this standard.3 For referencedASTM standards, visit theASTM website, www.astm.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 documen
16、t is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes 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 app
17、ropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ANSI Standards:4N13.30 Performance Criteria for Radiobio
18、assayN42.14 Calibration and Use of Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates ofRadionuclidesN42.23 Measurement QualityAssurance for Radioassay LaboratoriesAmerican National Standard Measurement andAssociatedInstrumentationANSI/IEEE-645IEEE-325 Standard Test Procedures f
19、or High Purity Germanium Detectors for Ionizing RadiationGermaniumGamma-Ray Detectors3. Terminology3.1 Except as otherwise defined herein, definitions of terms are as given in Terminology C859.4. Summary of Guide4.1 High-resolution germanium detectors and multichannel analyzers are used to ensure th
20、e identification of the gamma-rayemitting radionuclides that are present and to provide the best possible accuracy for quantitative activity determinations.4.2 For qualitative radionuclide identifications, the system must be energy calibrated. For quantitative determinations, thesystem must also be
21、shape and efficiency calibrated. The standard sample/detector geometries must be established as part of theefficiency calibration procedure.4.3 The soil samples typically need to be pretreated (for example, dried), weighed, and placed in a standard container. Forquantitative measurements, the dimens
22、ions of the container holding the sample and its placement in front of the detector mustmatch one of the efficiency-calibrated geometries. If multiple geometries can be selected, the geometry chosen should reflect thedetection limit and count rate limitations of the system. Qualitative measurements
23、may be performed in non-calibrated geometries.4.4 The identification of the radionuclides present is based on matching the energies of the observed gamma rays in the spectrumto computer-based libraries of literature references see Refs (14),(15),(16),(17), or (18).The quantitative determinations are
24、 basedon comparisons of observed count rates to previously obtained counting efficiency versus energy calibration data, and publishedbranching ratios for the radionuclides identified.5. Significance and Use5.1 Gamma-ray spectrometry of soil samples is used to identify and quantify certain gamma-ray
25、emitting radionuclides. Use ofa germanium semiconductor detector is necessary for high-resolution gamma-ray measurements.5.2 Much of the data acquisition and analysis can be automated with the use of commercially available systems that include bothhardware and software. For a general description of
26、the typical hardware in more detail than discussed in Section 67, see Ref (19).For best practices on set-up, calibration, and quality control of utilized spectrometry systems, see Practice D7282.5.3 Both qualitative and quantitative analyses may be performed using the same measurement data.5.4 The p
27、rocedures described in this guide may be used for a wide variety of activity levels, from natural background levelsand fallout-type problems, to determining the effectiveness of cleanup efforts after a spill or an industrial accident, to tracingcontamination at older production sites, where wastes w
28、ere purposely disposed of in soil. In some cases, the combination ofradionuclide identities and concentration ratios can be used to determine the source of the radioactive materials.5.5 Collecting samples and bringing them to a data acquisition system for analysis may be used as the primary method t
29、o detectdeposition of radionuclides in soil. For obtaining a representative set of samples that cover a particular area, see Practice C998.Soil can also be measured by taking the data acquisition system to the field and measuring the soil in place (in situ). In situmeasurement techniques are not dis
30、cussed in this guide.6. Interferences6.1 In complex mixtures of gamma-ray emitters, the degree of interference of one nuclide in the determination of another isgoverned by several factors. Interference will occur when the photopeaks from two separate nuclides overlap within the resolutionof the gamm
31、a-ray spectrometer. Most modern analysis software can deconvolute multiplets where the separation of any twoadjacent peaks is more than 0.5 FWHM (see Refs (20) and (21). For peak separations that are smaller than 0.5 FWHM, mostinterference situations can be resolved with the use of automatic interfe
32、rence correction algorithms (22).6.2 If the nuclides are present in the mixture in very unequal radioactive portions and if nuclides of higher gamma-ray energyare predominant, the interpretation of minor, less energetic gamma-ray photopeaks becomes difficult due to the high Comptoncontinuum and back
33、scatter.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.C1402 1726.3 True coincidence summing (also called cascade summing) occurs regardless of the overall count rate for any radionuclidethat emits two or more gamma ra
34、ys in coincidence. Cobalt-60 is an example where both a 1173-keV and a 1332-keV gamma rayare emitted from a single decay. If the sample is placed close to the detector, there is a finite probability that both gamma rays fromeach decay interact within the resolving time of the detector resulting in a
35、 loss of counts from both full energy peaks. Coincidencesumming and the resulting losses to the photopeak areas can be considerable (10 %) before a sum peak at an energy equal to thesum of the coincident gamma-ray energies becomes visible. Coincidence summing and the resulting losses to the two indi
36、vidualphotopeak areas can be reduced to the point of being negligible by increasing the source to detector distance or by using a smalldetector. Coincidence summing can be a severe problem if a well-type detector is used. See Test Methods E181 and (7) for moreinformation.6.4 Random summing is a func
37、tion of count rate (not dead time) and occurs in all measurements. The random summing rateis proportional to the total count squared and to the resolving time of the detector and electronics. For most systems, uncorrectedrandom summing losses can be held to less than 1 % by limiting the total counti
38、ng rate to less than 1000 count/s.counts/s. However,high-precision analyses can be performed at high count rates by the use of pileup rejection circuitry and dead-time correctiontechniques. Refer to Test Methods E181 for more information.7. Apparatus7.1 Germanium Detector AssemblyThe detector should
39、 have an active volume of greater than 50 cm3, with a full width at onehalf the peak maximum (FWHM) less than 2.0 keV for the cobalt-60 gamma ray at 1332 keV, certified by the manufacturer. Acharge-sensitive preamplifier should be an integral part of the detector assembly.7.2 Sample Holder AssemblyA
40、s reproducibility of results depends directly on reproducibility of geometry, the system shouldbe equipped with a sample holder that will permit using reproducible sample/detector geometries for all sample container typesthat are expected to be used at several different sample-to-detector distances.
41、7.3 ShieldThe detector assembly should be surrounded by a radiation shield made of material of high atomic numberproviding the equivalent attenuation of 100 mm (or more in the case of high background radiation) of low-activity lead. It isdesirable that the inner walls of the shield be at least 125 m
42、m distant from the detector surfaces to reduce backscatter andannihilation radiation. If the shield is made of lead or has a lead liner, the shield should have a graded inner shield of appropriatematerials, for example, 1.6 mm of cadmium or tin-lined with 0.4 mm of copper, to attenuate the induced 8
43、8-keV lead fluorescentX-rays. The shield should have a door or port for inserting and removing samples. The materials used to construct the shield shouldbe prescreened to ensure that they are not contaminated with unacceptable levels of natural or man-made radionuclides. The lowerthe desired detecti
44、on capability, the more important it is to reduce the background. For very low activity samples, the detectorassembly itself, including the preamplifer, should be made of carefully selected low background materials.7.4 High-Voltage Power/Bias SupplyThe bias supply required for germanium detectors us
45、ually provides a voltage up to65000 V and 1 to 100 A. The power supply should be regulated to 0.1 % with a ripple of not more than 0.01 %. Noise causedby other equipment should be removed with r-f filters and power line regulators.7.5 AmplifierA spectroscopy amplifier which is compatible with the pr
46、eamplifier. If used at high count rates, a model withpile-up rejection should be used. The amplifier should be pole-zeroed properly prior to use.7.6 Data Acquisition EquipmentA multichannel pulse-height analyzer (MCA) with a built-in or stand-alone analog-to-digitalconverter (ADC) compatible with th
47、e amplifier output and pileup rejection scheme. The MCA(hardwired or a computer-software-based) collects the data, provides a visual display, and stores and processes the gamma-ray spectral data. The four majorcomponents of an MCAare:ADC, memory, control, and input/output. TheADC digitizes the analo
48、g pulses from the amplifier. Theheight of these pulses represents energy deposited in the detector. The digital result is used by the MCAto select a memory location(channel number) which is used to store the number of events which have occurred at the energy. The MCA must also be able toextend the d
49、ata collection time for the amount of time that the system is dead while processing pulses (live time correction).7.7 Count Rate MeterIt is useful but not mandatory to have a means to measure the total count rate for pulses above theamplifier noise during the measurement. If not provided by the MCA, a separate count rate meter may be used for this purpose.In the absence of a rate meter, count rates that are too high to provide reliable results may also be detected by monitoring the systemdead time or peak resolution, or both.7.8 PulserRequired only if random summing
