Study on the Dissolution Behavior of UO₂ in the Na₂CO₃–H₂O₂ System Using a Flow-Through Dissolution Device

The CARBEX process, proposed in 2008, is a spent nuclear fuel (SNF) reprocessing process that relies on the alkaline environment of a Na2CO3–H2O2 system. In this work, we focused on the dissolution stage of the CARBEX process using a flow-through dissolution device to investigate the dissolution behavior of UO2 in the Na2CO3–H2O2 system and provide the dissolution rates of UO2 under different concentrations of Na2CO3 and H2O2. In addition, the 60Co-γ radiation source was used to simulate the radioactive environment during spent fuel reprocessing and to investigate the effect on the UO2 dissolution behavior in irradiation. The results show that the radiolysis products of water molecules react with excess H2O2 in solution to further generate •HO2. At the same time, H2O2 can also quench reductive radioactive dissolution products, increasing the oxidizing nature of the solution and thereby enhancing the dissolution rate of UO2 in a Na2CO3–H2O2 system. Finally, the dissolution process of UO2 in the Na2CO3–H2O2 system under irradiation conditions was summarized.