A comparison of carbon impurities in pre- and post-melt uranium Part 1: Scanning electron microscopy analysis

Abstract

Although C impurities in U have been studied for decades, fundamental questions regarding their incorporation, migration, and transformations during metal processing still exist. In two written Parts, we compare the chemical speciation, distributions, crystallography, and morphologies (e.g., size and shape) of C-containing impurities in U metal both before and after melting using high-resolution analytical electron microscopy (AEM). This first Part demonstrates the variability of carbide inclusions in U metal with respect to their chemical phases and morphologies as observed by scanning electron microscopy (SEM). A variety of inclusion types, such as the pill-shaped U monocarbide (UC), previously only hypothesized, are summarized. Additionally, delineation between hopper-shaped U carbonitride U(C,N) and dendritic U carbide inclusions is discussed in relationship to historic literature.