ASTM E481-23
(Practice)Standard Practice for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
Standard Practice for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
SIGNIFICANCE AND USE
3.1 This practice 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 its 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 (4-6) contain a general discussion of the two-reaction test method. In this practice, 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 parentheses 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) The decay constant, λ, is defined as ln(2) / t1/2 with units of sec–1, where t1/2 is the nuclide half-life in seconds.(C) Calculated using Eq 10.(D) In Fig. 1, Θ = 4ErkT/AΓ2 = 0.2 corresponds to the value for 109Ag for T = 293 K, ∑r = N0σr,max,T=0Kσr,max,T=0K = 31138.03 barn at 5.19 eV (13). The value of σr,max,T=0K = 31138.03 barns is calculated using the Breit-Wigner single-level resonance formula where the 109Ag atomic mass is A = 108.9047558 amu (14), the ENDF/B-VIII.0 (MAT = 4731) (13) resonance parameters are: resonance total width Γ = 0.1427333 eV, formation neutron width Γn = 0.0127333 eV, and radiative/decay width Γγ = 0.13 eV, with a resonance spin J=1, and the statistical spin factor where s1 = 1/2 and s2 = 1/2 are the spins of the two particles (neutron and 109Ag ground state (15)) forming resonance.
3.2 The advantages of this approach are the elimination of four 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; a...
SCOPE
1.1 This practice covers a suitable means of obtaining the thermal neutron fluence rate, or fluence, in nuclear reactor environments where the use of cadmium, as a thermal neutron shield as described in Test Method E262, is undesirable for reasons such as potential spectrum perturbations or due to temperatures above the melting point of cadmium.
1.2 The reaction 59Co(n,γ )60Co results in a well-defined gamma emitter having a half-life of 5.2711 years2 (8)3 (1).4 The reaction 109Ag(n,γ)110mAg results in a nuclide with a well-known, complex decay scheme with a half-life of 249.78 (2) 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 (SRM) 953.5 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 108 cm−2·s−1 to 3 × 1015 cm−2·s−1 can be measured. Two calculational practices are described in Section 9 for the determination of neutron fluence rates. The practice described in 9.3 may be used in all cases. This practice describes a means of measuring a Westcott neutron fluence rate in 9.2 (Note 1) by activation of cobalt- and silver-foil monitors (see Terminology E170). For the Wescott Neutron Fluence Convention method to be applicable, the measurement location must be well moderated and be well represented by a Maxwellian low-energy distribution and an (1/E) epithermal distribution. These conditions are usually only met in positions surrounded by hydrogenous moderator without nearby strongly multiplying or absorbing materials.
Note 1: Westcott fluence rate ...
General Information
Buy Standard
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: E481 − 23
Standard Practice 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/E) epithermal distribution. These conditions are usually only
met in positions surrounded by hydrogenous moderator with-
1.1 This practice covers a suitable means of obtaining the
out nearby strongly multiplying or absorbing materials.
thermal neutron fluence rate, or fluence, in nuclear reactor
`
environments where the use of cadmium, as a thermal neutron
NOTE 1—Westcott fluence rate 5v * n v dv
~ !
0 0
shield as described in Test Method E262, is undesirable for
1.3 The values stated in SI units are to be regarded as the
reasons such as potential spectrum perturbations or due to
standard, except in the case of nuclear data where the source
temperatures above the melting point of cadmium.
referenced units are retained in order to preserve the integrity
59 60
1.2 The reaction Co(n,γ ) Co results in a well-defined
of the referenced uncertainty values.
2 3 4
gamma emitter having a half-life of 5.2711 years (8) (1).
1.4 This standard does not purport to address all of the
109 110m
The reaction Ag(n,γ) Ag results in a nuclide with a
safety concerns, if any, associated with its use. It is the
well-known, complex decay scheme with a half-life of 249.78
responsibility of the user of this standard to establish appro-
(2) days (1). Both cobalt and silver are available either in very
priate safety, health, and environmental practices and deter-
pure form or alloyed with other metals such as aluminum. A
mine the applicability of regulatory limitations prior to use.
reference source of cobalt in aluminum alloy to serve as a
1.5 This international standard was developed in accor-
neutron fluence rate monitor wire standard is available from the
dance with internationally recognized principles on standard-
National Institute of Standards and Technology (NIST) as
ization established in the Decision on Principles for the
5
Standard Reference Material (SRM) 953. The competing
Development of International Standards, Guides and Recom-
activities from neutron activation of other isotopes are
mendations issued by the World Trade Organization Technical
eliminated, for the most part, by waiting for the short-lived
Barriers to Trade (TBT) Committee.
products to die out before counting. With suitable techniques,
8 −2 −1
thermal neutron fluence rate in the range from 10 cm ·s to
2. Referenced Documents
15 −2 −1
3 × 10 cm ·s can be measured. Two calculational practices 6
2.1 ASTM Standards:
are described in Section 9 for the determination of neutron
E170 Terminology Relating to Radiation Measurements and
fluence rates. The practice described in 9.3 may be used in all
Dosimetry
cases. This practice describes a means of measuring a Westcott
E177 Practice for Use of the Terms Precision and Bias in
neutron fluence rate in 9.2 (Note 1) by activation of cobalt- and
ASTM Test Methods
silver-foil monitors (see Terminology E170). For the Wescott
E181 Guide for Detector Calibration and Analysis of Radio-
Neutron Fluence Convention method to be applicable, the
nuclides in Radiation Metrology for Reactor Dosimetry
measurement location must be well moderated and be well
E261 Practice for Determining Neutron Fluence, Fluence
represented by a Maxwellian low-energy distribution and an
Rate, and Spectra by Radioactivation Techniques
E262 Test Method for Determining Thermal Neutron Reac-
tion Rates and Thermal Neutron Fluence Rates by Radio-
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
activation Techniques
Technology and Applications and is the direct responsibility of Subcommittee
E10.05 on Nuclear Radiation Metrology.
3. Significance and Use
Current edition approved June 1, 2023. Published July 2023. Originally approved
in 1973. Last previous edition approved in 2016 as E481 – 16. DOI: 10.1520/
3.1 This practice uses one monitor (cobalt) with a nearly 1/v
E0481-23.
2
absorption cross-section curve and a second monitor (silver)
One year is defined to be 365.242198 days (31 556 926 seconds) (1).
3
The value of uncertainty, in parentheses, refers to the corresponding last digits,
thus 14.958 (2) corresponds to 14.958 6 0.002.
4 6
The boldface numbers in parentheses refer to references listed at the end of this For referenced ASTM standard
...
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 − 16 E481 − 23
Standard Test Method Practice 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 Co(n,γ ) Co results in a well-defined gamma emitter having a
2 109 110m
half-life of 1925.28 days (1). The reaction Ag(n,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
3
is available from the National Institute of Standards and Technology (NIST) as Standard 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
9 −2 −1 15 −2 −1
out before counting. With suitable techniques, thermal neutron fluence rate in the range 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:
1
This test method practice 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 Oct. 1, 2016June 1, 2023. Published October 2016July 2023. Originally approved in 1973. Last previous edition approved in 20152016 as
E481 – 15.E481 – 16. DOI: 10.1520/E0481-16.10.1520/E0481-23.
4
The boldface numbers in parentheses refer to references listed at the end of this test method.
5
Standard Reference Material 953 is available from National Institute of Standards and Technology, U.S. Dept. of Commerce, Washington, DC 20234.
6
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
1
---------------------- Page: 1 ----------------------
E481 − 23
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
E262 Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation
Techniques
3. 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 integ
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.