Decontamination technique for decommissioning waste

The radioactive waste generated during the decommissioned commercial nuclear reactors has certain characteristic features, such as large volume, broad range of radioactivity, and mixed composition of different shapes and materials. A range of decontamination methods, including mechanical and chemical decontamination techniques are used as required depending on the contamination level and the condition of the waste. Decontamination comprises pre-treatment, main decontamination, and post-treatment processes. The authors have studied the effectiveness of the pre-treatment process. The decontamination performance of the REDOX and electrolytic decontamination processes after abrasive blasting was evaluated using BWRs specimens. Decontamination experiments with wet abrasive blasting were carried as before main decontamination. The test specimens were taken from BWRs to ensure characteristics like those of actual decommissioning waste. After removal of the oxide layer by wet abrasive blasting, the specimens were dissolved by Redox decontamination or electrolytic decontamination, and contamination was reduced to below the target exemption level. Results indicate that the maximum decontamination factor with wet abrasive blasting reached 100, and the time required for main decontamination was less than decontaminating with electrolytic decontamination or Redox only.