ASTM E481-03

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

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 E 262, 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 E 170). The reaction 59Co(n,)60Co results in a well-defined gamma emitter having a half-life of 1925.5 days (1). The reaction  109Ag(n,) 110mAg results in a nuclide with a complex decay scheme which is well known and having a half-life of 249.76 days (14). 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 cm2 s1 to 3 1015 cm2  s1  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 0
Westcott fluence rate = Equation 1 - v00n(v)dv.
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.

General Information

• Status: Historical
• Publication Date: 09-Feb-2003
• 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 E481-97 - Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
• Effective Date: 10-Feb-2003
• Replaced By: ASTM E481-10 - Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
• Effective Date: 01-Jan-2010
• Referred By: ASTM E944-19 - Standard Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance
• Effective Date: 10-Feb-2003
• Referred By: ASTM E261-16(2021) - Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
• Effective Date: 10-Feb-2003
• Referred By: ASTM E262-17 - Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques
• Effective Date: 10-Feb-2003
• Referred By: ASTM E1854-19 - Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
• Effective Date: 10-Feb-2003
• Referred By: ASTM E1005-21 - Standard Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance
• Effective Date: 10-Feb-2003

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:E481–03
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 1.3 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 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 (See Terminology E170). The
59 60 E170 TerminologyRelatingtoRadiationMeasurementsand
reaction Co(n,g) Co results in a well-defined gamma emitter
2 Dosimetry
having a half-life of 1925.5 days (1). The
109 110m
E177 Practice for Use of the Terms Precision and Bias in
reaction Ag(n,g˙) Ag results in a nuclide with a complex
ASTM Test Methods
decay scheme which is well known and having a half-life of
E181 TestMethodsforDetectorCalibrationandAnalysisof
249.76 days (14). Both cobalt and silver are available either in
Radionuclides
verypureformoralloyedwithothermetalssuchasaluminum.
E262 Test Method for DeterminingThermal Neutron Reac-
A reference source of cobalt in aluminum alloy to serve as a
tion Rates and Thermal Neutron Fluence Rates by Radio-
neutronfluenceratemonitorwirestandardisavailablefromthe
activation Techniques
National Institute of Standards and Technology (NIST) as
3
Standard Reference Material 953. The competing activities
3. Significance and Use
fromneutronactivationofotherisotopesareeliminated,forthe
3.1 The pertinent data for these two reactions are given in
most part, by waiting for the short-lived products to die out
Table 1. This test method uses one monitor (cobalt) with a
before counting. With suitable techniques, thermal neutron
9 −2 −1 15 −2 nearly1/vabsorptioncross-sectioncurveandasecondmonitor
fluence rate in the range from 10 cm ·s to 3 3 10 cm
−1 (silver) with a large resonance peak so that its resonance
·s can be measured. For this method to be applicable, the
integral is large compared to the thermal cross section. The
reactor must be well moderated and be well represented by a
equations are based on the Westcott formalism (3, 4) and
Maxwellian low-energy distribution and an (1/E) epithermal
determineaWestcott2200m/sneutronfluencerate nv andthe
0
distribution. These conditions are usually met in positions
Westcott epithermal index parameter r T/T . References 5,
=
0
surroundedbyhydrogenousmoderatorwithoutnearbystrongly
6, and 7 contain a general discussion of the two-reaction test
absorbing materials. Otherwise the true spectrum must be
method. In this test method, the absolute activities of both
calculated to obtain effective activation cross sections over all
cobaltandsilvermonitorsaredetermined.Thisdiffersfromthe
energies.
test method in the references wherein only one absolute
`
NOTE 1—Westcott fluence rate = v * n~v!dv.
0 0 activity is determined.
3.2 Theadvantagesofthistestmethodaretheeliminationof
three difficulties associated with the use of cadmium: (1) the
1
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear
perturbation of the field by the cadmium; (2) the inexact
Technology and Applications and is the direct responsibility of Subcommittee
cadmium cut-off energy; (3) the low melting temperature of
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.
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. the
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