The Anodic Reactions on Simulated Spent Fuel (SIMFUEL) in H₂O₂Solutions: Effect of Carbonate/Bicarbonate

Abstract

The anodic behavior of simulated nuclear fuel (SIMFUEL) in solutions containing H 2 O 2 and HCO 3 − /CO 3 2− has been studied electrochemically and using surface analytical techniques, in particular X-ray photoelectron spectroscopy. Two anodic reactions are possible, the oxidative dissolution of UO 2 and H 2 O 2 oxidation. The rates of both reactions are controlled by the chemical release of U VI surface species, and can both be increased by the addition of HCO 3 − /CO 3 2−. Under anodic conditions the dominant reaction is H 2 O 2 oxidation, although UO 2 dissolution may also be accelerated by the formation of a uranyl peroxocarbonate complex. Similarly, under open circuit (corrosion) conditions both UO 2 corrosion and H 2 O 2 decomposition are also controlled by the rate of release of U VI surface species which blocks access of H 2 O 2 to the underlying conductive U IV 1-2x U V 2x O 2+x surface. Presently, the balance between these two reactions is not known.