Chemical precipitation–based treatment of acidic wastewater generated by chemical decontamination of radioactive concrete

Abstract

Radionuclide-contaminated concrete can be turned into non-radioactive industrial waste through the sequential application of thermomechanical and chemical treatments. Herein, we examine the removal of 137Cs, 90Sr, and 60Co from complex acidic wastewater generated by chemical treatment, revealing that wastewater radioactivity due to these nuclides can be decreased to below the discharge criteria through the injection of potassium ferrocyanide and co-precipitation with BaSO4. In these processes, the concentration of Fe3+ in the wastewater significantly enhanced the removal of 137Cs via metal-ferrocyanide precipitation with effective hydroxide precipitation for 60Co, whereby additional Fe3+ was needed after the injection of potassium ferrocyanide. In the case of 90Sr, the nuclide formed an isomorphous sulphate by rapidly combining with Ba2+ in the BaSO4 lattice structure before particle growth. Furthermore, a large amount of BaSO4 will be required relatively to separate very low radioactivity of 90Sr, compared with high initial radioactivity. Thus, our work provides guidelines for reducing the volume of radioactive waste generated during nuclear facility decommissioning and should therefore help to decrease decommissioning cost.