Neutron Irradiated Uranium Silicides Studied by Neutron Diffraction and Rietveld Analysis

Abstract

The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U3Si and U3Si2 amorphous at temperatures below about 250 C [1], and that U3Si becomes mechanically unstable suffering rapid growth by plastic flow [2,3]. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier filtering analysis of the non-crystalline scattering component [4].