Reinforcement of cobalt leaching resistance of solidified sludge for disposal of radioactive sludge waste by hot isostatic pressing

Cobalt leaching resistance of the solidified radioactive sludge subject to disposal was evaluated. The sludge powders ((Fe 2 O 3 ), NiO, and Cr 2 O 3 ) with non-radioactive cobalt powder was homogeneously mixed with ferro frit and treated in hot isostatic pressing process. Although the mixing ratio of the ferro frit in total solidified sludge waste was less than 25% and heating temperature in HIP process was lower than 1000 °C, the cobalt leachability indices in all the solidified sludge were ranged from 13.9 to 18.4. The study showed the solidified sludge waste satisfied the leachability index criteria for waste disposal, which was six.