Catalytic effect of cesium on the oxidation behavior of cation exchange resins in Li2CO3-Na2CO3-K2CO3 melt

Abstract

After the treatment of liquid radioactive waste, there is a certain amount of Cs in the waste resin, and these Cs-doped resins are prone to volatilize during the thermal treatment process and cause radionuclide leakage. The molten salt oxidation (MSO) can effectively prevent the volatilization of toxic metal, especially the volatilization of Cs. Under nitrogen and air conditions, it is found that the oxidation behavior between Cs-doped and clean cation exchange resins (CERs) is quite different. In the presence of oxygen and molten carbonate salt, Cs₂CO₃ is generated by the destruction of functional groups in Cs-doped CERs. The Cs₂CO₃ in Na₂CO₃-K₂CO₃-Li₂CO₃ reacts with oxygen to form Li₂O₂, which reduces the content of S in residue from 26.33 to 13.38% in air conditions at 400 °C and promotes the generation of sulfate in the molten carbonate salt. The elements Cs and S in the Cs doped CERs spontaneously form thermally stable Cs₂SO₄ in the molten carbonate salt.

Keywords: Carbonate salt; Cation exchange resin; Cesium sulfate; Lithium peroxide, Radioactive waste; Molten salt oxidation.