The Influence of Corrosion Deposits on Uo2 Corrosion/dissolution

Abstract

The influence of acidic conditions on UO₂ fuel dissolution has been studied using electrochemical and surface analytical techniques such as Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The mechanism of UO₂ anodic dissolution changes for pH<5, since the solubility of U^VI increases substantially. Potentiostatic and Electrochemical Impedance Spectroscopy (EIS) in chloride or sulphate solutions in the pH range 0 to 3 show that the sulphate anion is more actively involved in the dissolution reaction than the chloride anion. Surface adsorption of sulphate to form an adsorbed uranyl sulphate complex appears to occur. In neutral chloride solutions containing silicate under constant current conditions (constant anodic dissolution rate), a uranyl silicate surface deposit is formed at local sites on the surface. This attributed to enhanced dissolution at these sites leading to acidic conditions underneath the deposit.