Phase separation of molybdenum, cesium and selenium from the borosilicate glass containing simulated nuclear wastes under a CO2-rich heating atmosphere

Molybdenum, cesium and selenium along with potassium-rich materials were phase-separated onto the surface from the borosilicate glass containing simulated high level radioactive wastes by heat treatment under a CO2 -containing atmosphere. The phase separation behaviors of potassium, molybdenum, cesium and selenium were characterized by FE-SEM, EDS, XPS and Raman analysis. These elements could be further extracted by leaching for recovery. The leaching results show that the extraction efficiencies of these elements under CO2-containing atmosphere were much higher than that under air atmosphere. Attempts were further made to investigate the effects of the melting temperature, melting time, the concentration of CO2 gas and the amount of potassium carbonate flux on the extraction efficiencies of molybdenum, cesium and selenium from the glass phase under the CO2-containing atmosphere. As a result, more than ca. 80% molybdenum, almost 100% selenium and ca. 50% cesium were extracted in the leachate from the highly simulated borosilicate glass under the CO2-containing heat treatment. It is expected that this technique can be extended to study the separation of other fission products by optimizing the process parameters in the future research. (C) 2019 Elsevier B.V. All rights reserved.