1、Designation: E1297 08 (Reapproved 2013)E1297 18Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Niobium1This standard is issued under the fixed designation E1297; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of revision, the 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 test method describes procedures for measuring reaction rates by the activation reactio
3、n 93Nb(n,n)93mNb.1.2 This activation reaction is useful for monitoring neutrons with energies above approximately 0.5 MeV and for irradiationtimes up to about 30 years.48 years (three half-lives), provided that the analysis methods described in Practice E261 are followed.1.3 With suitable techniques
4、, fast-neutron reaction rates for neutrons with energy distribution similar to fission neutrons can bedetermined in fast-neutron fluences above about 1016 cm2. In the presence of high thermal-neutron fluence rates (1012cm2s1),the transmutation of 93mNb due to neutron capture should be investigated.
5、In the presence of high-energy neutron spectra such asare associated with fusion and spallation sources, the transmutation of 93mNb by reactions such as (n,2n) may occur and shouldbe investigated.1.4 Procedures for other fast-neutron monitors are referenced in Practice E261.1.5 Fast-neutron fluence
6、rates can be determined from the reaction rates provided that the appropriate cross section informationis available to meet the accuracy requirements.1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard does n
7、ot purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.8 This int
8、ernational 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 World Trade Organization Technical Barriers to Trade (TBT) Co
9、mmittee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE170 Terminology Relating to Radiation Measurements and DosimetryE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE181 Test Methods for Detector Calibration and Analysis of RadionuclidesE
10、185 Practice for Design of Surveillance Programs for Light-Water Moderated Nuclear Power Reactor VesselsE261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation TechniquesE262 Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Ra
11、tes by RadioactivationTechniquesE456 Terminology Relating to Quality and StatisticsE844 Guide for Sensor Set Design and Irradiation for Reactor SurveillanceE944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor SurveillanceE1005 Test Method for Application and Analysis of Radio
12、metric Monitors for Reactor Vessel SurveillanceE1006 Practice for Analysis and Interpretation of Physics Dosimetry Results from Test Reactor Experiments1 This test method is under the jurisdiction of ASTM Committee E10 on Nuclear Technology and Applicationsand is the direct responsibility of Subcomm
13、ittee E10.05 onNuclear Radiation Metrology.Current edition approved Jan. 1, 2013June 1, 2018. Published January 2013August 2018. Originally approved in 1989. Last previous edition approved in 20082013 asE1297 08.E1297 08(2013). DOI: 10.1520/E1297-08R13.10.1520/E1297-18.2 For referencedASTM standards
14、, 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 document is not an ASTM standard and is intended only to provide the user of an ASTM s
15、tandard 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 appropriate. In all cases only the current versionof the standard as published by
16、ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1018 Guide for Application of ASTM Evaluated Cross Section Data File3. Terminology3.1 DefinitionsThe definitions stated in Terminology E17
17、0 and E456 are applicable to this test method.4. Summary of Test Method4.1 High purity niobium is irradiated in a neutron field producing radioactive 93mNb from the 93Nb(n,n)93mNb reaction. Themetastable state decays to the ground state by the virtual emission of 30 keV gamma rays that are all inter
18、nally converted givingrise to the actual emission of orbital electrons followed by X rays.4.2 Sources of the irradiated niobium are prepared for X ray or liquid scintillation counting.4.3 The X rays emitted as a result of the decay of 93mNb are counted, and the reaction rate, as defined in Practice
19、E261, iscalculated from the decay rate and irradiation conditions.4.4 The neutron fluence rate may then be calculated from the appropriate spectral-weighted neutron activation cross section asdefined by Practice E261.5. Significance and Use5.1 Refer to Practice E261 for a general discussion of the d
20、etermination of decay rates, reaction rates, and neutron fluence rateswith threshold detectors (1-29).3 Refer to Practice E1006, Practice E185 and Guide E1018 for the use and application of resultsobtained by this test method.(30-32)5.2 The half-life of 93mNb is 5730 616.1 (2)4 220 yearsdays5(3334)
21、and has a K X-ray emission probability of 0.10990.114426 0.0025 3.356 % per decay (3335). The K and K X-rays of niobium are at 16.521316.15216.52116.615 and18.61818.95318.60718.9852 keV, respectively.respectively (35). The recommended 93Nb (n,n)Nb(n,n)93mNb cross sectioncomes from the IRDF-90 Intern
22、ational Reactor Dosimetry and Fusion File (IRDFF version 1.05, cross section compendium (3436),was drawn from and is shown in Fig. 1the RRDF-98 . This nuclear data evaluation is part of the Russian Reactor Dosimetry File(RRDF), cross section evaluations (3537). The nuclear decay data referenced here
23、 are not taken from the latest dosimetryrecommended database (33) and is shown but are selected to be consistent with the nuclear data used in Fig. 1.the recommendedIRDFF evaluation.5.3 Chemical dissolution of the irradiated niobium to produce very low mass-per-unit area sources is an effective way
24、to obtainconsistent results. The direct counting of foils or wires can produce satisfactory results provided appropriate methods andinterpretations are employed. It is possible to use liquid scintillation methods to measure the niobium activity provided theradioactive material can be kept uniformly
25、in solution and appropriate corrections can be made for interfering activities.3 The boldface numbers in parentheses refer to the list of references at the end of this test method.4 The value of uncertainty, in parenthesis, refers to the corresponding last digits, thus 16.1(2) corresponds to 16.1 6
26、0.2, which corresponds to 16.1 6 1.24 %.5 One year is defined to be 365.242198 days 31556926 seconds in the source documents referenced (33).FIG. 1 IRDF-90RRDF/IRDFF-1.05 Cross Section Versus Energy for the 93Nb(n,n)93mNb ReactionE1297 1825.4 The measured reaction rates can be used to correlate neut
27、ron exposures, provide comparison with calculated reaction rates,and determine neutron fluences. Reaction rates can be determined with greater accuracy than fluence rates because of the currentuncertainty in the cross section versus energy shape.5.5 The 93Nb(n,n)93mNb reaction has the desirable prop
28、erties of monitoring neutron exposures related to neutron damage ofnuclear facility structural components. It has an energy response range corresponding to the damage function of steel and has ahalf-life sufficiently long to allow its use in very long exposures (up to about 4048 years). Monitoring l
29、ong exposures is useful indetermining the long-term integrity of nuclear facility components.6. Interferences6.1 Pure niobium in the forms of foil and wire is available and easily handled as a metal. When thin niobium is irradiated, itmay become brittle and fragile, thus requiring careful handling o
30、r encapsulation to prevent damage or loss of the niobium. Referto Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.6.2 There are some distinct advantages and limitations to three measurement techniques identified in 5.3. It is the responsibilityof the user to eval
31、uate these and determine the optimum technique for the situation.6.2.1 Low mass source X-ray spectrometry advantages include sufficient energy resolution to eliminate other X-ray emissions,stable long life sources, reduced interference fluorescence due to other radionuclides, small and precise backg
32、round corrections,and minimal X-ray source self-absorption corrections. Limitations are low counting efficiency, complex source preparation, anduse of hazardous chemicals.6.2.2 Direct X-ray spectrometry of metal (foil or wire) sources has the advantages of simple source preparation, stable long life
33、sources, sufficient energy resolution to eliminate other X-ray emissions, small and precise background corrections, and no use ofhazardous chemicals. Limitations are low counting efficiency, large X-ray source self-absorption corrections, larger corrections forinterference fluorescence due to the ot
34、her radionuclides, and source geometry control.6.2.3 Liquid scintillation counting advantages include very high detection efficiency, reproducible source preparation, and nosource self absorption corrections. Limitations include specialized calibration techniques to reduce interference from otherrad
35、ionuclides, limited source stability, use of hazardous chemicals, and disposal of hazardous chemical waste.7. Apparatus7.1 X-ray Spectrometer, using a Si(Li) detector or a Ge detector and a multichannel pulse-height analyzer. For more information,refer to Test Methods E181 and E1005.7.2 Precision Ba
36、lance, able to achieve the required accuracy.7.3 Beakers, 50 mL polyethylene; pycnometer (weighing bottle), 50 mL polyethylene; volumetric pipets, 10 L to 5 mL.7.4 Gamma Ray Spectrometer, using a Ge detector and a multichannel pulse-height analyzer. Refer to Test Method E181.7.5 Liquid Scintillation
37、 Counter.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where suchspecifications are
38、 available.6 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, any water used shall be understood to mean reagent water as defi
39、ned by TypeI of Specification D1193.8.3 Hydrofluoric AcidConcentrated (32M) hydrofluoric acid (HF).8.4 Nitric AcidConcentrated (16M) nitric acid (HNO3).8.5 Niobium MetalThe purity of the niobium is important in that no impurities (such as tantalum) should be present to producelong-lived radionuclide
40、s that interfere with the 93mNb activity determination.To avoid problems from tantalum, the niobium shouldhave the lowest tantalum content possible. Niobium metal in the form of foil and wire with tantalum content of about 5 ppm (partsper million) or less is obtainable and can be used under most con
41、ditions. The niobium material should be tested for interferingradioactivity by neutron activation techniques.8.6 Encapsulation MaterialThe encapsulation material (such as quartz, stainless steel, aluminum, etc.) should be selected toprevent corrosion of the niobium during irradiation and to be compa
42、tible with the irradiation environment and post-irradiation6 “Reagent Chemicals, American Chemical Society Specifications,” Am. Chemical Soc., Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society, see “Reagent Chemicals and Standards,” by Joseph Rosin
43、, D. Van Nostrand Co., Inc., New York, NY, and the “United States Pharmacopeia.”E1297 183handling. If thermal and epithermal neutron filters or shrouds are used, these materials (such as cadmium, tantalum, gadolinium,etc.) must also be compatible with the encapsulation and irradiation environment.8.
44、7 Analytical PaperAnalytical grade filter paper of uniform thickness (about 0.076 cm) and density (about 8 mg cm2). Thepaper can be cut or obtained precut to the desired size (usually between 0.5 and 1.5 cm diameter) that is compatible with theactivity concentration of the solution and the counting
45、conditions.The paper should be able to absorb as much liquid as is necessaryand not decompose from the acid. TFE-fluorocarbon rings with an inside diameter matching the outside diameter of the filter paperdisks so they fit together with light contact.8.8 Support and Cover MaterialsThin plastic film
46、and plastic tape materials are useful to support and cover the filter papersources. They should be strong enough to contain the sources and thin enough to minimize attenuation of the X rays.8.9 Source HolderAsource holder must be used to accurately and reproducibly position the sources for the count
47、ing geometryto be used. The source holder should be constructed of low density materials such as aluminum or plastic.8.10 Liquid Scintillation MaterialsVials, emulsion scintillant (xylene-based), chelating agent (di-2-ethylhexyl phosphoricacid).9. Procedure9.1 Determine the size and shape of the nio
48、bium sample being irradiated. Consider the convenience in handling and availableirradiation space. Ensure that sufficient 93mNb activity will be produced to permit accurate radioassay. Typically, samples of 0.2to 20 mg of niobium may be used, but a preliminary calculation of the expected production
49、of 93mNb will aid in selecting theappropriate mass for the irradiation.9.2 Accurately weigh the niobium sample being irradiated.9.3 Encapsulate the niobium sample so that it can be retrieved and identified following the irradiation. Record the sampleidentification, sample weight, and exact details of the encapsulation. Shroud the niobium with neutron filter material if necessary.If the thermal-to-fast neutron fluence rate ratio is high (greater than 5) or the tantalum impurity is high (greater than 10 ppm), useneutron filter materials, if possibl
