Study on Advanced Volume Reduction Focusing on Fly Ash Washing solution of Decontamination Wastes, etc. ~Comparison of Column and Batch Tests on Copper Ferrocyanide~

Abstract

Japanese government policy mandates that decontamination waste, mainly contaminated by ¹³⁷Cs, will undergo final disposal outside of Fukushima prefecture. Post-incineration fly ash, heat-treated with calcium chloride, concentrates Cs as cesium chloride (CsCl) in melting fly ash (MFA). Washing MFA dissolves CsCl, but the solution contains interfering ions like Na, K, and Rb. This study focused on estimating the saturation adsorption amount of copper ferrocyanide (CFC) using ion exchange theory on batch test and column tests with a model solution of MFA washing solution. The model solution was prepared with initial [K]₀ = 3.0 mol/L and [K/Cs]₀ = 1,000. batch tests were conducted in varying L/S ratios, Column tests were carried out using controlled flow rates, measuring Cs in the filtrates. Results showed that the saturation adsorption amount varied with the L/S ratio and salt concentration ratios on batch tests. These findings highlight the need for careful consideration of MFA composition and flow rates to optimize volume reduction. Column tests indicated higher adsorption was achieved at lower flow rates, estimation based on ion exchange theory indicated that the K'Cs/K ratio on the low adsorption rate side was the dominant factor.