ASTM-E481:2010 Edition

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E481-10 Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver

Published By	Publication Date	Number of Pages
ASTM	2010	7

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Description

ASTM E481-10

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

ASTM E481

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.

Keywords

activation; cobalt; dosimetry; foil; silver; thermal neutron; Cobalt- and silver-foil monitors; Fluence; Neutron activation reactions; Neutron flux/fluence; Radioactivation–fast neutron flux; Silver-foil monitors; Thermal neutron flux

ICS Code

ICS Number Code 17.240 (Radiation measurements)

DOI: 10.1520/E0481-10

PDF Catalog

PDF Pages	PDF Title
1	Scope Referenced Documents Significance and Use
2	Apparatus Materials and Manufacture Procedure TABLE 1
3	Calculation TABLE 2 TABLE 3
4	FIG. 1
5	TABLE 4
6	Precision and Bias Keywords REFERENCES

Additional information

Standard Title	E481-10 Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
Published Code	ASTM
Publication Date	2010
Pages Count	7