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

摘要

The weathering and corrosion of depleted uranium (DU) forms a complex series of oxidation reactions,ultimately resulting in metaschoepite,U0_3 centre dot 2H_2O.The present work focused on studying the dissolution rate of synthetic U0_3 centre dot 2H_2O using batch and flow-through reactors.Under acidic conditions (pH=4.4-5.4),atmospheric C0_2,room temperature,and 0.1 mionic 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 UO_3 centre dot 2H_2O in the first hour,followed by fluctuations in uranium concentration before equilibrium was attained after 3000 h.