Determination of α and f for k₀-NAA in irradiation sites with high thermalized neutrons

Abstract

At the irradiation sites in a research reactor where neutrons are well thermalized, the "bare" irradiation methods for a and f determinations that are incorporated in the KAYZERO^®/SOLCOI^® v4.0 package seem to be unworkable. It is a fact that when carrying out the determination of a and f at the PN-3 irradiation site of the JRR-3M research reactor (Tokai, Japan) using the KAYZERO software, unacceptable results were obtained from experiment to experiment for a ranging from 0.10 to 0.999 and f ranging from 70 to 9999. The "Cd ratio" for a gold monitor in the PN-3 site is about 300. These unacceptable results have indicated the need for the application of Cd methods that are based on "Cd-covered" irradiation and "Cd-ratio" measurements at certain suitable and available monitors. Such Cd methods have not been incorporated into the KAYZERO v4.0 software. Therefore, computational and experimental procedures of the "Cd-covered" method for a and the "Cd-ratio" method for f determination have been presented in this paper. The PN-2 irradiation site of the JRR-3M reactor where the neutron thermalization is not high has a Cd ratio for gold of about 26. The commonly used "bare" irradiation methods can be applied together with the Cd methods so that all results may be presented as comparable data. The results of a and f determinations that were carried out in the PN-2 and PN-3 irradiation sites are presented.