ASTM E481-15

Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver

SIGNIFICANCE AND USE
3.1 This test method uses one monitor (cobalt) with a nearly 1/v absorption cross-section curve and a second monitor (silver) with a large resonance peak so that its resonance integral is large compared to the thermal cross section. The pertinent data for these two reactions are given in Table 1. The equations are based on the Westcott formalism ((2, 3) and Practice E261) and determine a Westcott 2200 m/s neutron fluence rate nv0 and the Westcott epithermal index parameter  . References 4, 5, and 6 contain a general discussion of the two-reaction test method. In this test method, the absolute activities of both cobalt and silver monitors are determined. This differs from the test method in the references wherein only one absolute activity is determined.  (A) The numbers in parenthesis following given values are the uncertainty in the last digit(s) of the value; 0.729 (8) means 0.729 ± 0.008, 70.8(1) means 70.8 ± 0.1.(B) A 2200 m/s cross section (E = 0.0253 eV, T = 20°C) was taken from the sources indicated in Ref (9).(C) Cross section uncertainty data is taken from Ref (7) , the cross section comes from the other reference.(D) Calculated using Eq 10.(E) Cross section uncertainty comes from convariance data provided in the cross section source. The other reference indicates the source of the cross section.(F) In Fig. 1, Θ = 4ErkT/AΓ 2 = 0.2 corresponds to the value for  109Ag for T = 293 K, ∑r = N0σr, max. σr, max=29999 barn at 5.19 eV (13) .  
3.2 The advantages of this test method are the elimination of three difficulties associated with the use of cadmium: (1) the perturbation of the field by the cadmium; (2) the inexact cadmium cut-off energy; (3) the low melting temperature of cadmium. In addition, the reactivity changes accompanying the rapid insertion and removal of cadmium may prohibit the use of the cadmium-ratio method. However, the self-shielding corrections remain important unless the concentrations of cobalt and silver are small. Studies indicate that ...
SCOPE
1.1 This test method covers a suitable means of obtaining the thermal neutron fluence rate, or fluence, in well moderated nuclear reactor environments where the use of cadmium, as a thermal neutron shield as described in Test Method E262, is undesirable because of potential spectrum perturbations or of temperatures above the melting point of cadmium.  
1.2 This test method describes a means of measuring a Westcott neutron fluence rate (Note 1) by activation of cobalt- and silver-foil monitors (See Terminology E170). The reaction  59Co(n,γ )60Co results in a well-defined gamma emitter having a half-life of 1925.28 days (1)2. The reaction  109Ag(n,γ)110mAg results in a nuclide with a complex decay scheme which is well known and having a half-life of 249.76 days (1). Both cobalt and silver are available either in very pure form or alloyed with other metals such as aluminum. A reference source of cobalt in aluminum alloy to serve as a neutron fluence rate monitor wire standard is available from the National Institute of Standards and Technology (NIST) as Standard Reference Material 953.3 The competing activities from neutron activation of other isotopes are eliminated, for the most part, by waiting for the short-lived products to die out before counting. With suitable techniques, thermal neutron fluence rate in the range from 109 cm−2 · s−1 to 3 × 1015 cm−2  · s−1  can be measured. For this method to be applicable, the reactor must be well moderated and be well represented by a Maxwellian low-energy distribution and an (1/E) epithermal distribution. These conditions are usually met in positions surrounded by hydrogenous moderator without nearby strongly absorbing materials. Otherwise the true spectrum must be calculated to obtain effective activation cross sections over all energies.
Note 1: Westcott fluence rate    
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 This standard does not purpo...

General Information

• Status: Historical
• Publication Date: 31-May-2015
• ICS: 17.240 - Radiation measurements
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: E10 - Nuclear Technology and Applications
• Drafting Committee: E10.05 - Nuclear Radiation Metrology

Relations

• Replaces: ASTM E481-10 - Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
• Effective Date: 01-Jun-2015
• Referred By: ASTM E1005-21 - Standard Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance
• Effective Date: 01-Jun-2015
• Referred By: ASTM E944-19 - Standard Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance
• Effective Date: 01-Jun-2015
• Referred By: ASTM E261-16(2021) - Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
• Effective Date: 01-Jun-2015
• Referred By: ASTM E262-17 - Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques
• Effective Date: 01-Jun-2015
• Referred By: ASTM E1854-19 - Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
• Effective Date: 01-Jun-2015

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E481 − 15
StandardTest Method for
Measuring Neutron Fluence Rates by Radioactivation of
1
Cobalt and Silver
This standard is issued under the fixed designation E481; 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 1.3 The values stated in SI units are to be regarded as the
standard.
1.1 This test method covers a suitable means of obtaining
1.4 This standard does not purport to address all of the
the thermal neutron fluence rate, or fluence, in well moderated
safety concerns, if any, associated with its use. It is the
nuclear reactor environments where the use of cadmium, as a
responsibility of the user of this standard to establish appro-
thermal neutron shield as described in Test Method E262,is
priate safety and health practices and determine the applica-
undesirable because of potential spectrum perturbations or of
bility of regulatory limitations prior to use.
temperatures above the melting point of cadmium.
1.2 This test method describes a means of measuring a
2. Referenced Documents
Westcott neutron fluence rate (Note 1) by activation of cobalt-
4
2.1 ASTM Standards:
and silver-foil monitors (SeeTerminology E170).The reaction
E170Terminology Relating to Radiation Measurements and
59 60
Co(n,γ ) Co results in a well-defined gamma emitter having
Dosimetry
2 109 110m
ahalf-lifeof1925.28days (1) .Thereaction Ag(n,γ) Ag
E177Practice for Use of the Terms Precision and Bias in
resultsinanuclidewithacomplexdecayschemewhichiswell
ASTM Test Methods
known and having a half-life of 249.76 days (1). Both cobalt
E181Test Methods for Detector Calibration andAnalysis of
andsilverareavailableeitherinverypureformoralloyedwith
Radionuclides
other metals such as aluminum.Areference source of cobalt in
E261Practice for Determining Neutron Fluence, Fluence
aluminum alloy to serve as a neutron fluence rate monitor wire
Rate, and Spectra by Radioactivation Techniques
standard is available from the National Institute of Standards
E262Test Method for Determining Thermal Neutron Reac-
3
and Technology (NIST) as Standard Reference Material 953.
tion Rates and Thermal Neutron Fluence Rates by Radio-
The competing activities from neutron activation of other
activation Techniques
isotopes are eliminated, for the most part, by waiting for the
short-lived products to die out before counting. With suitable 3. Significance and Use
9
techniques, thermal neutron fluence rate in the range from 10
3.1 Thistestmethodusesonemonitor(cobalt)withanearly
−2 −1 15 −2 −1
cm ·s to3×10 cm ·s can be measured. For this
1/v absorption cross-section curve and a second monitor
method to be applicable, the reactor must be well moderated
(silver) with a large resonance peak so that its resonance
and be well represented by a Maxwellian low-energy distribu-
integral is large compared to the thermal cross section. The
tion and an (1/E) epithermal distribution. These conditions are
pertinent data for these two reactions are given in Table 1.The
usuallymetinpositionssurroundedbyhydrogenousmoderator
equations are based on the Westcott formalism ((2, 3) and
without nearby strongly absorbing materials. Otherwise the
Practice E261) and determine a Westcott 2200 m/s neutron
true spectrum must be calculated to obtain effective activation
fluence rate nv and the Westcott epithermal index parameter
0
cross sections over all energies.
r=T/T .References 4, 5,and 6containageneraldiscussionof
0
`
NOTE 1—Westcott fluence rate 5v * n v dv. the two-reaction test method. In this test method, the absolute
~ !
0
0
activities of both cobalt and silver monitors are determined.
Thisdiffersfromthetestmethodinthereferenceswhereinonly
1
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear
one absolute activity is determined.
Technology and Applications and is the direct responsibility of Subcommittee
E10.05 on Nuclear Radiation Metrology.
3.2 Theadvantagesofthistestmethodaretheeliminationof
CurrenteditionapprovedJune1,2015.PublishedJuly2015.Originallyapproved
three difficulties associated with the use of cadmium: (1) the
in 1973. Last previous edition approved in 2010 as E481–10. DOI: 10.1520/
E0481-15.
2 4
Theboldfacenumbersinparenthesesrefertoreferenceslistedattheendofthis For referenced ASTM standards, visit the ASTM website, www.astm.org, or
test method. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standard Reference Material 953 is available from National Institute of Standards volume information, refer to the standard’s Document Summary page on
Standards and Technology, U.S. Dept. of Commerce, Washington, DC 20234. th
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E481 − 10 E481 − 15
Standard Test Method for
Measuring Neutron Fluence Rates by Radioactivation of
1
Cobalt and Silver
This standard is issued under the fixed designation E481; 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
1.1 This test method covers a suitable means of obtaining the thermal neutron fluence rate, or fluence, in well moderated nuclear
reactor environments where the use of cadmium, as a thermal neutron shield as described in Test Method E262, is undesirable
because of potential spectrum perturbations or of temperatures above the melting point of cadmium.
1.2 This test method describes a means of measuring a Westcott neutron fluence rate (Note 1) by activation of cobalt- and
59 60
silver-foil monitors (See Terminology E170). The reaction reaction Co(n,γ ) Co results in a well-defined gamma emitter
2 109 110m
having a half-life of 1925.28 days (1).) . The reaction reaction Ag(n,Ag(n,γ)γ˙) Ag results in a nuclide with a complex
decay scheme which is well known and having a half-life of 249.76 days (1). Both cobalt and silver are available either in very
pure form or alloyed with other metals such as aluminum. A reference source of cobalt in aluminum alloy to serve as a neutron
fluence rate monitor wire standard is available from the National Institute of Standards and Technology (NIST) as Standard
3
Reference Material 953. The competing activities from neutron activation of other isotopes are eliminated, for the most part, by
waiting for the short-lived products to die out before counting. With suitable techniques, thermal neutron fluence rate in the range
9 −2 −1 15 −2 −1
from 10 cm · s to 3 × 10 cm · s can be measured. For this method to be applicable, the reactor must be well moderated
and be well represented by a Maxwellian low-energy distribution and an (1/E) epithermal distribution. These conditions are usually
met in positions surrounded by hydrogenous moderator without nearby strongly absorbing materials. Otherwise the true spectrum
must be calculated to obtain effective activation cross sections over all energies.
`
*
NOTE 1—Westcott fluence rate 5v n v dv.
0 ~ !
0
1.3 The values stated in SI units are to be regarded as the standard.
1.4 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.
2. Referenced Documents
4
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 Test Methods for Detector Calibration and Analysis of Radionuclides
E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
E262 Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation
Techniques
3. Significance and Use
3.1 The pertinent data for these two reactions are given in Table 1. This test method uses one monitor (cobalt) with a nearly
1/v absorption cross-section curve and a second monitor (silver) with a large resonance peak so that its resonance integral is large
1
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 Jan. 1, 2010June 1, 2015. Published May 2010July 2015. Originally approved in 1973. Last previous edition approved in 20032010 as
E481 – 03.E481 – 10. DOI: 10.1520/E0481-10.10.1520/E0481-15.
2
The boldface numbers in parentheses refer to references listed at the end of this test method.
3
Standard Reference Material 953 is available from National Institute of Standards and Technology, U.S. Dept. of Commerce, Washington, DC 20234.
4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
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