Nuclear and dosimetric features of an isotopic neutron source

Conceptual design for a new heterogeneous 241Am-9Be neutron source assembly using SOURCES4C-MCNPX hybrid simulations

In this study, an approach to simulate a novel variable-yield heterogeneous ²⁴¹Am-⁹Be was proposed with a hybrid use of SOURCES4C and MCNPX codes, and its energy spectrum and neutron emission yield were simulated. In these simulations, the energy spectra of the alpha particles emitted from the americium source and the neutrons produced within the beryllium and oxygen contents as a result of ⁹Be(α,n) and ^17,18O(α,n) reactions were calculated with SOURCES4C whilst the neutron transport from neutron production points to the space outside the source assembly were performed with the MCNPX code. The neutron energy spectrum and neutron emission yield for two different configurations of single-rod and multi-rod sources (i.e., americium or americium oxide rods in beryllium medium) were compared to a source of homogeneous americium (or its oxides) and beryllium mixture. The proposed heterogeneous geometry was aimed to provide a neutron source with a variable neutron yield, easy-to-shut down and easy-to-waste process features. The results confirmed that the homogeneous source represented the largest neutron yield compared to single- and multi-rod geometries. However, the neutron yield in heterogenous geometry could be altered by varying the number of americium (or americium oxide) rods to reach the desired neutron yield.