A new coupled non-thermal plasma and sorption method for treatment of liquid radioactive wastes: Design and on-site application to Chornobyl NPP-derived wastes

Higher activity liquid wastes pose a significant management challenge at nuclear sites, and there is a strong drive to develop cost-effective (and more sustainable) waste treatment solutions that can remove radioactive and other contaminants from these liquid radioactive wastes (LRW) prior to their discharge or final storage/disposal. Here, results are presented from an on-site trial of a coupled non-thermal plasma / sorption-based LRW treatment system at the “Dibrova” Object in the Chornobyl Exclusion Zone. Over 2m³ of Cs-137 and Sr-90 contaminated LRW from settling tanks used for the holding of tailings and drain water from Chornobyl Building № 5 and deactivation solutions (used in the liquidation efforts following the 1986 Chornobyl disaster) were treated. The coupled treatment process removed greater than 90 % of Cs-137 and Sr-90 from the most contaminated liquids (containing 75 Bq/kg (Cs-137) and 195 Bq/kg (Sr-90)), generating a low mass (<100g ) iron-rich solid residue suitable for onward storage/disposal. Treatment efficiencies for other waste components (e.g. nitrites, phosphates and COD) were equivalent to or exceeded those previously reported for treatment of environmental liquid wastes by similar Advanced Oxidation Processes. The power requirements of the system (due to the pulsed nature of the plasma generated) were relatively low, at 10 kWh, for a LRW treatment rate of 15 - 20 L/h. The system can be operated remotely in autonomous mode, and its modular, easily transportable nature means that the process can be readily adapted for various on-site treatment scenarios.