ASTM E266-23

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Designation: E266 − 17 E266 − 23
Standard Test Method for
Measuring Fast-Neutron Reaction Rates by Radioactivation
of Aluminum
This standard is issued under the fixed designation E266; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
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1.1 This test method covers procedures measuring reaction rates by the activation reaction Al(n,α) 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 2two days (for longer irradiations, or when there are significant variations in reactor power during the irradiation, see
Practice E261).
6 −2 −1
1.3 With suitable techniques, fission-neutron fluence rates above 10 cm ·s can be determined.
1.4 Detailed procedures for other fast neutron detectors are referenced in Practice E261.
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
2.1 ASTM Standards:
E170 Terminology Relating to Radiation Measurements and Dosimetry
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E181 Guide for Detector Calibration and Analysis of Radionuclides in Radiation Metrology for Reactor Dosimetry
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
This test method is under the jurisdiction of ASTM Committee E10 on Nuclear Technology and Applications and is the direct responsibility of Subcommittee E10.05
on Nuclear Radiation Metrology.
Current edition approved Aug. 1, 2017June 1, 2023. Published October 2017June 2023. Originally approved in 1965. Last previous edition approved in 20112017 as
E266 – 11.E266 – 17. DOI: 10.1520/E0266-17.10.1520/E0266-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E266 − 23
3. Terminology
3.1 Definitions:
3.1.1 Refer to Terminologies E170 and E456.
4. Summary of Test Method
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4.1 High-purity aluminum is irradiated in a neutron field, thereby producing radioactive Na from the Al(n,α) Na activation
reaction.
4.2 The gamma rays emitted by the radioactive decay of Na are counted (see Test Methods Guide E181) and the reaction rate,
as defined by Practice E261, is calculated from the decay rate and irradiation conditions.
4.3 The neutron fluence rate above about 6.5 MeV can then be calculated from the spectral-weighted neutron activation cross
section as defined by Practice E261.
5. Significance and Use
5.1 Refer to Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.
5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors.
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5.3 Pure aluminum in the form of foil or wire is readily available and easily handled. Al has an abundance of 100 % (1)). .
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5.4 Na has a half-life of 14.958 (2) h (2) and emits gamma rays with energies of 1.368630 (5) and 2.754049 (5)(13) MeV (2).
5.5 Fig. 1 shows a plot of the RussianInternational Reactor Dosimetry File (RRDF)and Fusion File (IRDFF-II) cross section (3,
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4) versus neutron energy for the fast-neutron reaction Al(n,α) Na (3) along with a comparison to the current experimental
database (5, 6). 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 (7).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 Al(n,α) reaction. Refer to
Guide E1018 for recommended sources for the tabulated dosimetry cross sections.
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5.6 Two competing activities, Al (2.25 (2) minute half-life) and Mg, Mg (9.458 (12) minute half-life), are formed in the
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reactions Al(n,γ) Al and Al(n,p) Mg, respectively, but these can be eliminated by waiting 2 h before counting.
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FIG. 1 Al(n,α) Na Cross Section, from RRDF-2008/IRDFF-1.05IRDFF-II Library, with EXFOR Experimental Data
The boldface numbers in parentheses refer to a list of References at the end of this standard.
The value of uncertainty, in parenthesis, refers to the corresponding last digits, thus 14.958 (2) corresponds to 14.958 6 0.002.
E266 − 23
6. Apparatus
6.1 NaI(T1) or High Resolution Gamma-Ray Spectrometer. Spectrometer—Because ofDue to its high resolution, the germanium
detector is useful when contaminant activities are present (see Test Methods Guide E181 and Test Method E1005).
6.2 Precision Balance, able to achieve the required accuracy.
7. Materials
7.1 The purity of the aluminum is important. No impurities should be present that produce long-lived gamma-ray-emitting
radionuclides having gamma-ray energies that interfere with the Na determination. Discard aluminum that contains such
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impurities or that contains quantities of Na sufficient to interfere, through thermal-neutron capture, with Na determination. The
presence of these impurities should be determined by activation analysis since spectrographically pure aluminum may contain a
contaminant not detectable by the emission spectrograph. If the Na content of the irradiated samples is determined from the
emission rate of the 2.754049 MeV gamma ray, the probability of interference from contaminant gamma rays is much less than
if the 1.368630 MeV gamma ray is used.
7.2 Encapsulating Materials—Brass, stainless steel, copper, aluminum, quartz, or vanadium have been used as primary
encapsulating materials. The container should be constructed in such a manner that it will not create significant flux perturbation
and that it may be opened easily, especially if the capsule is to be opened remotely (see Guide E844).
8. Procedure
8.1 Decide on the size and shape of aluminum sample to be irradiated. This is influenced by the irradiation space and the expected
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production of Na. Calculate the expected production rate of Na from the activation equation described in Section 9, and adjust
sample size and irradiation time so that the Na may be accurately counted. A trial irradiation is recommended.
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8.2 Determine a suitable irradiation time (see 8.1). Since Na has a 14.958 h half-life, the Na activity will approach equilibrium
after a day of irradiation.
8.3 Weigh the sample.
8.4 Irradiate the sample for the predetermined time period. Record the power level and any changes in power during the
irradiation, the time at the beginning and end of the irradiation, and the relative position of the monitors in the irradiation facility.
8.5 After irradiation, the sample should be thoroughly rinsed in warm water. This will remove any Na surface contamination
produced during irradiation.
8.6 Check the sample for activity from cross-contamination by other irradiated materials. Clean, if necessary, and reweigh.
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8.7 Analyze the sampl
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