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ASTM-E481:2003 Edition

ASTM-E481:2003 Edition

$40.63

E481-03 Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver

Published By Publication Date Number of Pages
ASTM 2003 7
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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 59 Co( n, ) 60 Co results in a well-defined gamma emitter having a half-life of 1925.5 days (1) . The reaction 109 Ag( n, ) 110m Ag 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 10 9 cm 2 s 1 to 3 10 15 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 0

Westcott fluence rate = Equation 1 – v 0 0 n(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.

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

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