Cs-137 and Cs-134 removal from radioactive ash using washing-electrokinetic equipment

To remove more than 85% of Cs-137 and Cs-134 from radioactive ash through a washing-electrokinetic technology, many washing and electrokinetic experiments at a laboratory scale were carried out to obtain the optimum reagent type, its concentration, and the decontamination time. Pilot-sized washing-electrokinetic equipment suitable to the radioactive ash generated in Fukushima Japan was manufactured. In addition, to remove more than 93% of Cs-137 and Cs-134 from the washed ash, electrokinetic decontamination experiments using 50 L pilot-sized electrokinetic equipment were carried out. When the initial Cs-137 concentration of radioactive ash was 41.8 Bq/g, the removal efficiency of Cs-137 in the radioactive ash after three washings was 89.1%. Additionally, the required electrokinetic decontamination time to decontaminate the Cs-137 concentration below 2.0 Bq/g was 10 days, and at that time, the removal efficiency of the Cs-137 was 95.3%. Also, when the initial Cs-134 concentration of radioactive ash was 31.5 Bq/g, the removal efficiency of Cs-134 in the radioactive ash after three washings was 89.0%. In addition, the required electrokinetic decontamination time to decontaminate the Cs-134 concentration below 2.0 Bq/g was 8 days, and at that time, the removal efficiency of Cs-137 was 94.4%. It was conclusively found that 87-89% of the Cs-134 and Cs-137 in the radioactive ash was removed by three washings, and the radioactive ash contaminated with 30-40 Bq/g of Cs-134 and Cs-137 needs to be decontaminated with electrokinetic equipment for 8-10 days after three washings to reach below 2.0 Bq/g. (C) 2013 Elsevier Ltd. All rights reserved.