ASTM-E266 › Historical Revision Information
Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Aluminum
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Scope
1.1 This test method covers procedures measuring reaction rates by the activation reaction 27Al(n,)24Na.
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, see Practice E 261).
1.3 With suitable techniques, fission-neutron fluence rates above 106cm2s1 can be determined.
1.4 Detailed procedures for other fast neutron detectors are referenced in Practice E 261.
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 and health practices and determine the applicability of regulatory limitations prior to use.
Significance and Use
Refer to Guide E 844
Refer to Practice E 261
Pure aluminum in the form of foil or wire is readily available and easily handled.
24Na has a half-life of 14.951 h (1)3 and emits gamma rays with energies of 1.368.633 and 2.754028 MeV (2).
Fig. 1 shows a plot of cross section versus neutron energy for the fast-neutron reaction 27Al(n,α)24Na from the IRDF2002 dosimetry cross section library(3). This figure is for illustrative purposes only to indicate the range of response of the 27Al(n,α) reaction. Refer to Guide E 1018
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.
FIG. 1 27Al(n,α)24Na Cross Section
Keywords
activation; activation reaction; aluminum; cross section; dosimetry; fast-neutron monitor; neutron metrology; pressure vessel surveillance; reaction rate; ICS Number Code 17.240 (Radiation measurements); 27.120.30 (Fissile materials and nuclear fuel technology)
To find similar documents by ASTM Volume:
12.02 (Nuclear (II), Solar, and Geothermal Energy)
To find similar documents by classification:
17.240 (Radiation measurements Including dosimetry Radiation protection, see 13.280)
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Document Number
ASTM-E266-07
Revision Level
2007 EDITION
Status
Superseded
Modification Type
Revision
Publication Date
June 1, 2007
Document Type
Test Method
Page Count
3 pages
Committee Number
E10.05