ASTM E266-17 Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Aluminum.pdf
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1、Designation: E266 17Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Aluminum1This standard is issued under the fixed designation E266; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 covers procedures measuring reactionrates by the activation reaction27Al(n,)24Na.1.2 This activation r
3、eaction is useful for measuring neutronswith energies above approximately 6.5 MeV and for irradiationtimes up to about 2 days (for longer irradiations, or when thereare significant variations in reactor power during theirradiation, see Practice E261).1.3 With suitable techniques, fission-neutron flu
4、ence ratesabove 106cm2s1can be determined.1.4 Detailed procedures for other fast neutron detectors arereferenced in Practice E261.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establis
5、h appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for
6、 theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE177 Practice for Use of the Terms Prec
7、ision and Bias inASTM Test MethodsE181 Test Methods for Detector Calibration and Analysis ofRadionuclidesE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE456 Terminology Relating to Quality and StatisticsE844 Guide for Sensor Set Design and Irradi
8、ation forReactor SurveillanceE944 Guide for Application of Neutron Spectrum Adjust-ment Methods in Reactor SurveillanceE1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel SurveillanceE1018 Guide for Application of ASTM Evaluated CrossSection Data File3. Termino
9、logy3.1 Definitions:3.1.1 Refer to Terminologies E170 and E456.4. Summary of Test Method4.1 High-purity aluminum is irradiated in a neutron field,thereby producing radioactive24Na from the27Al(n,)24Naactivation reaction.4.2 The gamma rays emitted by the radioactive decay of24Na are counted (see Test
10、 Methods E181) and the reactionrate, as defined by Practice E261, is calculated from the decayrate and irradiation conditions.4.3 The neutron fluence rate above about 6.5 MeV can thenbe calculated from the spectral-weighted neutron activationcross section as defined by Practice E261.5. Significance
11、and Use5.1 Refer to Guide E844 for the selection, irradiation, andquality control of neutron dosimeters.5.2 Refer to Practice E261 for a general discussion of thedetermination of fast-neutron fluence rate with threshold de-tectors.5.3 Pure aluminum in the form of foil or wire is readilyavailable and
12、 easily handled.27Al has an abundance of 100 %(1)3.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applicationsand is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved Aug. 1, 2017. Published October 2017
13、. Originallyapproved in 1965. Last previous edition approved in 2011 as E266 11. DOI:10.1520/E0266-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards
14、Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of References at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accorda
15、nce with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.146 5.424Na has a half-life of 14.9
16、58 (2)4h (2) and emitsgamma rays with energies of 1.368630 (5) and 2.754049 (5)MeV(2).5.5 Fig. 1 shows a plot of the Russian Reactor DosimetryFile (RRDF) cross section (3, 4) versus neutron energy for thefast-neutron reaction27Al(n,)24Na (3) along with a compari-son to the current experimental datab
17、ase (5, 6). This RRDF-2008 cross section is identical to what is found in the latestInternational Atomic Energy Agency (IAEA) InternationalReactor Dosimetry and Fusion File, IRDFF-1.05 (7). While theRRDF-2008 and IRDFF-1.05 cross sections extend fromthreshold up to 60 MeV, due to considerations of t
18、he availablevalidation data, the energy region over which this standardrecommends use of this cross section for reactor dosimetryapplications only extends from threshold at 4.25 MeV up to20 MeV. This figure is for illustrative purposes and is used toindicate the range of response of the27Al(n,) reac
19、tion. Referto Guide E1018 for recommended sources for the tabulateddosimetry cross sections.5.6 Two competing activities,28Al and27Mg, are formed inthe reactions27Al(n,)28Al and27Al(n,p)27Mg, respectively,but these can be eliminated by waiting 2 h before counting.6. Apparatus6.1 NaI(T1) or High Reso
20、lution Gamma-Ray Spectrometer.Because of its high resolution, the germanium detector isuseful when contaminant activities are present (see Test Meth-ods E181 and E1005).6.2 Precision Balance, able to achieve the required accu-racy.7. Materials7.1 The purity of the aluminum is important. No impuritie
21、sshould be present that produce long-lived gamma-ray-emittingradionuclides having gamma-ray energies that interfere withthe24Na determination. Discard aluminum that contains suchimpurities or that contains quantities of23Na sufficient tointerfere, through thermal-neutron capture, with24Na determi-na
22、tion. The presence of these impurities should be determinedby activation analysis since spectrographically pure aluminummay contain a contaminant not detectable by the emissionspectrograph. If the24Na content of the irradiated samples isdetermined from the emission rate of the 2.754049 MeVgamma ray,
23、 the probability of interference from contaminantgamma rays is much less than if the 1.368630 MeV gamma rayis used.7.2 Encapsulating MaterialsBrass, stainless steel, copper,aluminum, quartz, or vanadium have been used as primaryencapsulating materials. The container should be constructedin such a ma
24、nner that it will not create significant fluxperturbation and that it may be opened easily, especially if thecapsule is to be opened remotely (see Guide E844).8. Procedure8.1 Decide on the size and shape of aluminum sample to beirradiated. This is influenced by the irradiation space and theexpected
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