ASTM-E481 Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver

Show Complete Document History

Document Center Inc. is an authorized dealer of ASTM standards.
The following bibliographic material is provided to assist you with your purchasing decision:

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



Changes from the previous issue

A redline edition is available for this document, with all changes visible. Ask Document Center Inc. for more information.


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 Test 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).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

1.3 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.


activation; cobalt; dosimetry; foil; silver; thermal neutron;; ICS Number Code 17.240 (Radiation measurements); 27.120.30 (Fissile materials and nuclear fuel technology)

To find similar documents by ASTM Volume:

12.02 (Nuclear (II), Solar, and Geothermal Energy)

To find similar documents by classification:

17.240 (Radiation measurements Including dosimetry Radiation protection, see 13.280)

27.120.30 (Fissile materials and nuclear fuel technology Including raw materials Radioactive wastes, see 13.030.30)

This document comes with our free Notification Service, good for the life of the document.

This document is available in either Paper or PDF format.

Document Number


Revision Level




Modification Type


Publication Date

Oct. 15, 2016

Document Type

Test Method

Page Count

7 pages

Committee Number