Kinetic Studies of Synthetic Metaschoepite under Acidic Conditions in Batch and Flow Experiments

The weathering and corrosion of depleted uranium (DU) forms a complex series of oxidation reactions, ultimately resulting in metaschoepite, UO3·2H2O. The present work focused on studying the dissolution rate of synthetic UO3·2H2O using batch and flow-through reactors. Under acidic conditions (pH = 4.4−5.4), atmospheric CO2, room temperature, and 0.1 m ionic strength, the log solubility product, log K sp = 5.26 at equilibrium and a pH-dependent rate law R 0 = (0.30 ± 0.15)[H+]0.83±0.1 were established. For consistency, these results were incorporated into the computer program PHREEQC 2.6, and the experimental conditions were simulated. There is generally good agreement between the experimental results and the modeled results. Batch experiments revealed a fast dissolution rate of UO3·2H2O in the first hour, followed by fluctuations in uranium concentration before equilibrium was attained after 3000 h.