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Significance and Use
5.1 Refer to Guide for the selection, irradiation, and quality control of neutron dosimeters.
5.2 Refer to Practice for a general discussion of the determination of fast-neutron fluence rate with threshold detectors.
5.3 Pure aluminum in the form of foil or wire is readily available and easily handled. 27Al has an abundance of 100 % ().
5.4 24Na has a half-life of 14.958 (2) h ( and emits gamma rays with energies of 1.368630 (5) and 2.754049 (5) MeV )(. )
5.5 shows a plot of the Russian Reactor Dosimetry File (RRDF) cross section (versus neutron energy for the fast-neutron reaction 27Al(n,α) 24Na , )( along with a comparison to the current experimental database )(. This RRDF-2008 cross section is identical to what is found in the latest International Atomic Energy Agency (IAEA) International Reactor Dosimetry and Fusion File, IRDFF-1.05 , )(. While the RRDF-2008 and IRDFF-1.05 cross sections extend from threshold up to 60 MeV, due to considerations of the available validation data, the energy region over which this standard recommends use of this cross section for reactor dosimetry applications only extends from threshold at ~4.25 MeV up to 20 MeV. This figure is for illustrative purposes and is used to indicate the range of response of the 27Al(n,α) reaction. Refer to Guide ) for recommended sources for the tabulated dosimetry cross sections.
FIG. 1 27Al(n,α)24Na Cross Section, from RRDF-2008/IRDFF-1.05 Library, with EXFOR Experimental Data
5.6 Two competing activities, 28Al and 27Mg, are formed in the reactions 27Al(n,γ) 28Al and 27Al(n,p) 27Mg, respectively, but these can be eliminated by waiting 2 h before counting.
1.1 This test method covers procedures measuring reaction rates by the activation reaction 27Al(n,α)24 Na.
1.2 This activation reaction is useful for measuring neutrons with energies above approximately 6.5 MeV and for irradiation times up to about 2 days (for longer irradiations, or when there are significant variations in reactor power during the irradiation, see Practice ).
1.3 With suitable techniques, fission-neutron fluence rates above 106 cm−2·s−1 can be determined.
1.4 Detailed procedures for other fast neutron detectors are referenced in Practice .
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
E170 Terminology Relating to Radiation Measurements and Dosimetry
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E181 Test Methods for Detector Calibration and Analysis of Radionuclides
E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
E456 Terminology Relating to Quality and Statistics
E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance
E944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance
E1005 Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance
E1018 Guide for Application of ASTM Evaluated Cross Section Data File
ICS Number Code 17.240 (Radiation measurements); 27.120.30 (Fissile materials and nuclear fuel technology)
|Link to Active (This link will always route to the current Active version of the standard.)|
ASTM E266-17, Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Aluminum, ASTM International, West Conshohocken, PA, 2017, www.astm.orgBack to Top