Phase transformation of iron oxides and oxohydroxides in high temperature aqueous media

Oxide layers grown on steels immersed in high temperature aqueous media play a foremost role in activity transport and the build-up of out-core radiation fields. Modelling of these processes require therefore a detailed description of the complex nature of these layers. Thus, Lister's out-core model assumed a Potter-Mann type of oxide layer and used the corresponding oxide-layer parameters to describe radioactivity accumulation on out-core structural steels. In more recent models developed, interactions between colloidal iron oxides and zirconium dioxide have also been included. As compared to low temperature electrochemically generated thin oxide layers, relatively less precise information has been gathered about the structure and morphology of hydrothermally grown oxide layers. The present paper aims at describing the fundamental role of the aqueous medium in defining the most important features of these oxides. (author). 6 figs., 43 refs