Decontamination of radioactive metal wastes using underwater microwave plasma

As nuclear power plants (NPPs) operate, the levels of radioactively contaminated oxide films are increased at the surface of the metal components of these plants. The Chalk River Unidentified Deposit (CRUD) is one such radioactive waste. Decontamination of CRUD is an essential task because radionuclides such as cobalt-60 (60Co; γ-emitter) can be deposited in the CRUD and react with the inverse spinel nickel ferrite. Hence, decontaminating the CRUD is an essential yet challenging process. Compared with conventional techniques, underwater microwave plasma was developed to provide high reliability and low environmental impact because the plasma system does not require external additives. In addition, the formation of highly reactive species such as radicals available to remove the deposited radioactive isotopes and underwater conditions of microwave plasma decontamination systems can reduce the risk of radioactive exposure during the decommissioning and decontamination of NPPs. This study demonstrated that the removal efficiency of cobalt of the microwave plasma system is 96.9%, which can be a new decontamination technique associated with the underwater cutting of metal wastes during the NPPs decommissioning process.