In nuclear power plant, there were many contaminated tanks dispose of radioactive fluid waste. These tanks are made of stainless-steel, and corrosion can occur when tanks are exposed to radioactive fluid waste containing moisture for a long time. Therefore, those sludge waste including radionuclide should be collected, solidified, and disposed of. If sludge can be melted, sludge can be easily solidified. However, melting points of sludge components (Fe2O3, NiO, Cr2O3) are very high as 1565, 1955, and 2435 , respectively. Therefore, melting sludge is difficult. If a solidification auxiliary material such as cement or asphalt is used to help solidify, solidification can easily occur, but cement and asphalt are vulnerable to heat. Vitrification using glass material can be solidification method, but the waste loading ratio of glass material is higher than 50%. High waste loading ratio is weakness in terms of volume reduction of waste. In this study, ferro frit powder (Na2O, K2O, CaO, Al2O3, B2O3, SiO2, ZnO) is used as solidification auxiliary material. When ferro frit powder mixed with sludge material are melted in sludge material, melted ferro frit powder can stick sludge material and can solidify sludge material without melting. Sludge can be solidified by using ferro frit powder with a smaller waste loading ratio than the vitrification method. However, since the waste loading ratio of the solidification auxiliary material is small, if ferro frit powder is not uniformly distributed between sludge powder, solidification may not be performed properly. Although the mixing ratio between sludge and ferro frit in solidified sludge is same, when the distribution of ferro frit powder in sludge is non-homogeneous, the difference in chemical and physical characteristics as compressive strength and leaching resistance can be observed in solidified sludge. As the ferro frit mixing ratio in the site where ferro frit exists was relatively high, the melting point of the mixed powder (sludge+ferro frit) decreased, and the mixed powder could not maintain its shape and melted. In the case of the area where ferro frit does not exist, since only the stainless-steel oxide sludge exists, sludge was not melted, and the shape was maintained. However, it was confirmed that the leaching resistance was lowered by visually observing the color change of the leachate within a short period of time (about 2 hours) when solidified sludge was immersed in the leachate.

• Ki Joon Kang(Ulsan National Institute of Science and Technology (UNIST))
• Sia Hwang(Ulsan National Institute of Science and Technology (UNIST))
• Hee Reyoung Kim(Ulsan National Institute of Science and Technology (UNIST)) Corresponding author