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ASTM E 481 : 2016

Superseded
Superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

View Superseded by
superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
Available format(s)

Hardcopy , PDF

Superseded date

21-07-2023

Language(s)

English

Published date

24-10-2016

1.1This 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.

1.2This 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 Equation E0481-16_1

1.3The values stated in SI units are to be regarded as the standard.

1.4This 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.

Committee
E 10
DocumentType
Test Method
Pages
7
PublisherName
American Society for Testing and Materials
Status
Superseded
SupersededBy
Supersedes

ASTM E 944 : 2019 Standard Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance
ASTM E 1005 : 2021 Standard Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance
ASTM E 1854 : 2019 Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
ASTM E 262 : 2017 Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques

ASTM E 177 : 1990 : REV A : R1996 Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
ASTM E 181 : 2017 Standard Test Methods for Detector Calibration and Analysis of Radionuclides
ASTM E 170 : 2020 Standard Terminology Relating to Radiation Measurements and Dosimetry
ASTM E 181 : 2023 Standard Guide for Detector Calibration and Analysis of Radionuclides in Radiation Metrology for Reactor Dosimetry
ASTM E 261 : 2016 Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
ASTM E 170 : 2023 Standard Terminology Relating to Radiation Measurements and Dosimetry
ASTM E 261 : 2016 : R2021 Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques

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