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ASTM E481

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

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Organization: ASTM
Publication Date: 1 October 2016
Status: active
Page Count: 7
ICS Code (Fissile materials and nuclear fuel technology): 27.120.30
ICS Code (Radiation measurements): 17.240
scope:

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 Test Method E262, is undesirable because of potential spectrum perturbations or of temperatures above the melting point of cadmium.

This test method describes a means of measuring a Westcott neutron fluence rate (Note 1) by activation of cobaltand 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 = v0f*0 `n(v)dv.

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

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 The boldface numbers in parentheses refer to references listed at the end of this test method.

Document History

ASTM E481
October 1, 2016
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
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...
June 1, 2015
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
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...
January 1, 2010
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
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...
February 10, 2003
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
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...
June 10, 1997
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver
1. 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...
January 1, 1986
Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver
A description is not available for this item.
March 31, 1978
STANDARD METHOD OF MEASURING NEUTRON-FLUX DENSITY BY RADIOACTIVATION OF COBALT AND SILVER
A description is not available for this item.

References

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