ASTM E481-10
(Test Method)Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
SIGNIFICANCE AND USE
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 compared to the thermal cross section. The equations are based on the Westcott formalism (2, 3) and determine a Westcott 2200 m/s neutron fluence rate nv0 and the Westcott epithermal index parameter r
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 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). 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. 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.
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Designation: E481 − 10
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 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
1.1 This test method covers a suitable means of obtaining
standard.
the thermal neutron fluence rate, or fluence, in well moderated
nuclear reactor environments where the use of cadmium, as a
1.4 This standard does not purport to address all of the
thermal neutron shield as described in Method E262,is
safety concerns, if any, associated with its use. It is the
undesirable because of potential spectrum perturbations or of
responsibility of the user of this standard to establish appro-
temperatures above the melting point of cadmium.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.2 This test method describes a means of measuring a
Westcott neutron fluence rate (Note 1) by activation of cobalt-
2. Referenced Documents
and silver-foil monitors (See Terminology E170). The reac-
4
59 60
2.1 ASTM Standards:
tion Co(n,γ ) Co results in a well-defined gamma emitter
2
E170Terminology Relating to Radiation Measurements and
having a half-life of 1925.28 days (1). The reac-
109 110m
Dosimetry
tion Ag(n,γ˙) Ag results in a nuclide with a complex
E177Practice for Use of the Terms Precision and Bias in
decay scheme which is well known and having a half-life of
ASTM Test Methods
249.76 days (1). Both cobalt and silver are available either in
E181Test Methods for Detector Calibration andAnalysis of
verypureformoralloyedwithothermetalssuchasaluminum.
Radionuclides
A reference source of cobalt in aluminum alloy to serve as a
E262Test Method for Determining Thermal Neutron Reac-
neutronfluenceratemonitorwirestandardisavailablefromthe
tion Rates and Thermal Neutron Fluence Rates by Radio-
National Institute of Standards and Technology (NIST) as
3
activation Techniques
Standard Reference Material 953. The competing activities
fromneutronactivationofotherisotopesareeliminated,forthe
3. Significance and Use
most part, by waiting for the short-lived products to die out
before counting. With suitable techniques, thermal neutron 3.1 The pertinent data for these two reactions are given in
9 −2 −1 15 −2
Table 1. This test method uses one monitor (cobalt) with a
fluence rate in the range from 10 cm ·s to3×10 cm
−1
·s can be measured. For this method to be applicable, the nearly1/vabsorptioncross-sectioncurveandasecondmonitor
(silver) with a large resonance peak so that its resonance
reactor must be well moderated and be well represented by a
Maxwellian low-energy distribution and an (1/E) epithermal integral is large compared to the thermal cross section. The
equations are based on the Westcott formalism (2, 3) and
distribution. These conditions are usually met in positions
surroundedbyhydrogenousmoderatorwithoutnearbystrongly determineaWestcott2200m/sneutronfluenceratenv andthe
0
absorbing materials. Otherwise the true spectrum must be
Westcott epithermal index parameter r =T/T . References 4,
0
calculated to obtain effective activation cross sections over all
5, and 6 contain a general discussion of the two-reaction test
energies.
method. In this test method, the absolute activities of both
cobaltandsilvermonitorsaredetermined.Thisdiffersfromthe
test method in the references wherein only one absolute
1
activity is determined.
This test method is under the jurisdiction ofASTM Committee E10 on Nuclear
Technology and Applicationsand is the direct responsibility of Subcommittee
3.2 Theadvantagesofthistestmethodaretheeliminationof
E10.05 on Nuclear Radiation Metrology.
three difficulties associated with the use of cadmium: (1) the
CurrenteditionapprovedJan.1,2010.PublishedMay2010.Originallyapproved
in 1973. Last previous edition approved in 2003 as E481–03. DOI: 10.1520/
E0481-10.
2 4
Theboldfacenumbersinparenthesesrefertoreferenceslistedattheendofthis For referenced ASTM standards, visit the ASTM website, www.astm.org, or
test method. contact ASTM Customer Service at service@astm.org. 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. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:E481–03 Designation:E481–10
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Thistestmethodcoversasuitablemeansofobtainingthethermalneutronfluencerate,orfluence,inwellmoderatednuclear
reactor environments where the use of cadmium, as a thermal neutron shield as described in 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,g ) Co results in a well-defined gamma emitter having a
110m
2 109 Ag(n,g˙)
half-life of 1925.51925.28 days (1). The reaction Ag(n,g˙ ) Ag results in a nuclide with a complex decay scheme
which is well known and having a half-life of 249.76 days (14(1). Both cobalt and silver are available either in very pure form
or alloyed with other metals such as aluminum.Areference source of cobalt in aluminum alloy to serve as a neutron fluence rate
monitorwirestandardisavailablefromtheNationalInstituteofStandardsandTechnology(NIST)asStandardReferenceMaterial
3
953. The competing activities from neutron activation of other isotopes are eliminated, for the most part, by waiting for the
9 −2
short-lived products to die out before counting.With suitable techniques, thermal neutron fluence rate in the range from 10 cm ·
−1 15 −2 −1
s to 3 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 = v * 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
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
comparedtothethermalcrosssection.TheequationsarebasedontheWestcottformalism((2,3,4)anddetermineaWestcott2200
m/s neutron fluence rate nv and the Westcott epithermal index parameter r T/T . References . References 4, 5, 6, and 76
=
0 0
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 Feb. 10, 2003. Published March 2003. Originally approved in 1973T. Last previous edition approved in 1997 as E481–97. DOI:
10.1520/E0481-03.
Current edition approved Jan. 1, 2010. Published May 2010. Originally approved in 1973. Last previous edition approved in 2003 as E481–03. DOI: 10.1520/E0481-10.
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
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
volume information, refer to the standard’s Documen
...
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