ASTM E2971-16(2020)
(Test Method)Standard Test Method for Determination of Effective Boron-10 Areal Density in Aluminum Neutron Absorbers using Neutron Attenuation Measurements
Standard Test Method for Determination of Effective Boron-10 Areal Density in Aluminum Neutron Absorbers using Neutron Attenuation Measurements
SIGNIFICANCE AND USE
5.1 The typical use of this test method is determination of 10B areal density in aluminum neutron absorber materials used to control criticality in systems such as: spent nuclear fuel dry storage canisters, transfer/transport nuclear fuel containers, spent nuclear fuel pools, and fresh nuclear fuel transport containers.
5.2 Areal density measurements are also used in the investigation of the uniformity in 10B spatial distribution.
5.3 The expected users of this standard include designers, suppliers, neutron absorber users, testing labs, and consultants in the field of nuclear criticality analysis.
5.4 Another known method used to determine areal density of 10B in aluminum neutron absorbers is an analytical chemical method as mentioned in Practice C1671. However, the analytical chemical method does not measure the “effective” 10B areal density as measured by neutron attenuation.
SCOPE
1.1 This test method is intended for quantitative determination of effective boron-10 (10B) areal density (mass per area of 10B, usually measured in grams-10B/cm2 ) in aluminum neutron absorbers. The attenuation of a thermal neutron beam transmitted through an aluminum neutron absorber is compared to attenuation values for calibration standards allowing determination of the effective 10B areal density. This test is typically performed in a laboratory setting. This method is valid only under the following conditions:
1.1.1 The absorber contains 10B in an aluminum or aluminum alloy matrix.
1.1.2 The primary neutron absorber is 10B.
1.1.3 The test specimen has uniform thickness.
1.1.4 The test specimen has a testing surface area at least twice that of the thermal neutron beam’s surface cross-sectional area.
1.1.5 The calibration standards of uniform composition span the range of areal densities being measured.
1.1.6 The areal density is between 0.001 and 0.080 grams of 10B per cm2.
1.1.7 The thermalized neutron beam is derived from a fission reactor, sub-critical assembly, accelerator or neutron generator.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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.
1.4 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.
General Information
Relations
Standards Content (Sample)
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.
Designation: E2971 − 16 (Reapproved 2020)
Standard Test Method for
Determination of Effective Boron-10 Areal Density in
Aluminum Neutron Absorbers using Neutron Attenuation
Measurements
This standard is issued under the fixed designation E2971; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method is intended for quantitative determina-
10 mendations issued by the World Trade Organization Technical
tion of effective boron-10 ( B) areal density (mass per area of
10 10 2 Barriers to Trade (TBT) Committee.
B, usually measured in grams- B/cm ) in aluminum neu-
tron absorbers. The attenuation of a thermal neutron beam
2. Referenced Documents
transmitted through an aluminum neutron absorber is com-
2.1 ASTM Standards
pared to attenuation values for calibration standards allowing
determination of the effective B areal density. This test is C1671Practice for Qualification and Acceptance of Boron
Based Metallic NeutronAbsorbers for Nuclear Criticality
typically performed in a laboratory setting. This method is
valid only under the following conditions: Control for Dry Cask Storage Systems andTransportation
Packaging
1.1.1 The absorber contains B in an aluminum or alumi-
E1316Terminology for Nondestructive Examinations
num alloy matrix.
1.1.2 The primary neutron absorber is B.
3. Terminology
1.1.3 The test specimen has uniform thickness.
1.1.4 The test specimen has a testing surface area at least
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
twice that of the thermal neutron beam’s surface cross-
Terminology E1316.
sectional area.
4. Summary of Test Method
1.1.5 The calibration standards of uniform composition
span the range of areal densities being measured.
4.1 In this test method, aluminum neutron absorbers are
1.1.6 Thearealdensityisbetween0.001and0.080gramsof
placed in a thermal neutron beam and the number of neutrons
10 2
B per cm .
transmitted through the material in a known period of time is
1.1.7 The thermalized neutron beam is derived from a
counted. The neutron count can be converted to B areal
fission reactor, sub-critical assembly, accelerator or neutron
density by performing the same test on a series of appropriate
generator.
calibration standards and comparing the results.
1.2 The values stated in SI units are to be regarded as
4.2 This test method uses a beam of neutrons with the
standard. No other units of measurement are included in this
neutron energy spectrum thermalized by an appropriate mod-
standard.
erator. Other methods such as neutron diffraction may be used
1.3 This standard does not purport to address all of the to generate a thermal neutron beam.
safety concerns, if any, associated with its use. It is the
4.3 A beam of thermal neutrons shall be derived from a
responsibility of the user of this standard to establish appro-
fission reactor, sub-critical assembly, accelerator or neutron
priate safety, health, and environmental practices and deter-
generator.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
5. Significance and Use
dance with internationally recognized principles on standard-
5.1 The typical use of this test method is determination of
B areal density in aluminum neutron absorber materials used
This test method is under the jurisdiction of ASTM Committee E07 on
Nondestructive Testing and is the direct responsibility of Subcommittee E07.05 on
Radiology (Neutron) Method. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2020. Published December 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2014. Last previous edition approved in 2016 as E2971–16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2971-16R20. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2971 − 16 (2020)
to control criticality in systems such as: spent nuclear fuel dry 7.1.7 A thermal neutron beam with a cross-sectional area
2 2
storage canisters, transfer/transport nuclear fuel containers, between 0.75 cm and 6.0 cm . The diameter of the beam
spent nuclear fuel pools, and fresh nuclear fuel transport should not exceed the active area of the neutron detector.
containers.
8. Hazards
5.2 Areal density measurements are also used in the inves-
tigation of the uniformity in B spatial distribution. 8.1 This test method does not address radiation safety. It is
the responsibility of the user of this test method to establish
5.3 The expected users of this standard include designers,
appropriate safety procedures, if necessary.
suppliers, neutron absorber users, testing labs, and consultants
in the field of nuclear criticality analysis.
9. Calibration and Standardization
5.4 Another known method used to determine areal density
10 9.1 A series of standards with uniform, homogenous, and
of Binaluminumneutronabsorbersisananalyticalchemical
accurately known B areal densities is necessary for quanti-
methodasmentionedinPracticeC1671.However,theanalyti-
tative interpretation of the counting data acquired in the
calchemicalmethoddoesnotmeasurethe“effective” Bareal
attenuation measurements. If the standards are not chemically
density as measured by neutron attenuation.
homogenous, the user of this standard must demonstrate that
the uniformity of the sample’s B is sufficient to meet the
6. Interferences
intention of this standard. These standards shall include B
6.1 Counts not associated with attenuation by the sample
arealdensitiesspanningtherangeofarealdensitiesexpectedin
shall be accounted for by measuring and incorporating back-
the test specimens. Calibration standards must have a testing
ground readings. Background reading will vary depending on
surface area at least twice that of the thermal neutron beam’s
the set up of the electronics of the system and the presence/
cross-sectional area.
absence of high energy photons.
9.2 The number of standards used shall take into consider-
6.2 Measuredcountratesapproachingthebackgroundcount
ation the magnitude and range of the sample’s target areal
rate may limit the abilities of a system to accurately measure
densityandrequiredaccuracyofthemeasurement.Aminimum
highly attenuating samples.
of three standards shall be used. The facility, calibration
standards, and the test samples’ areal densities should be
6.3 Coincidence loss may occur in the B detector(s) when
considered when determining the spacing of the calibration
the neutron count rate is too high.
areal densities. For example, when using a poly-energetic
beam, the optimal spacing of the calibration standard’s areal
7. Apparatus
densities will not be uniform.
7.1 The essential features required for areal density mea-
9.3 Aluminum shim plate(s) may be required with the
surement are the following:
standards to simulate the aluminum in the test specimen.
7.1.1 Source of thermal neutrons of an appropriate intensity
Because the absorption and scattering cross-sections of alumi-
to obtain the desired counting statistics in a reasonable time
num are very small, exact replication of the aluminum in the
period while not saturating the detector. If the counting rate is
testspecimensisnotcritical.Scatteringplaysaveryminorrole
too high, pulses can pile up, causing counts to be lost. The
in neutron attenuation measurements. The standards shall be
detector time constant in most modern counting circuits is
shimmed to ensure an equivalent or larger scattering contribu-
sufficiently small to accommodate up to2×10 CPM.
tion than the test specimen.
However, checks should be made to ensure that the system
resolving time is not excessive.
9.4 If the material used for calibration standards contains
7.1.2 A neutron beam intensity monitor for correction of neutron absorbing or scattering nuclides not present in the test
neutron intensity fluctuations.
specimens, or vice versa, the effect of these nuclides on the
7.1.3 A collimator long enough to result in a thermal accuracy of the measurements shall be addressed.
neutronbeamwithaminimalbeamdivergencethatwillreduce
scattering contributions and B measurement variability with 10. Procedure
samplethickness.Thecollimatormaybeevacuated,filledwith
10.1 The following procedure describes the method used to
air, or an inert gas.
measure the calibration standards as well as the samples.
7.1.4 A physical support, preferably adjustable, to mount
Calibration,background,andbeamintensityshallbemeasured
the standard and the test specimens in the neutron beam.
each time a set of samples are undergoing investigation, so the
7.1.5 A neutron detector, usually a boron tri-fluoride (BF )
measurement of these values is also described as part of the
filleddetectortube.InBF detectors,thepulseamplitudesfrom
procedure. This particular approach measures all values as
neutrons are much larger than the pulses produced by gamma
counts per measurement period.
radiation. The pulse height discriminator is normally readily
10.2 Prepare
...
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