[en] For safety evaluation about the geological disposal system, the leakage of radionuclides with groundwater flow is estimated by considering the groundwater flow through the manmade and natural barriers. In such an estimate, we should also consider the influence of cement materials used for the construction of the disposal facility system. Cement material including high alkalinity alters groundwater condition up to 13 in pH and dissolves numerous silicate materials, which release silicic acid to groundwater. Since this groundwater mixes with natural groundwater downstream, supersaturated silicic acid will be produced with the decrease of pH to 8 around the repository system. Thus, in this study, the behavior of supersaturated silicic acid in a flow system was examined by using the column packed with amorphous silica particles under the condition of constant hydraulic head. The packed length is 20 mm or 40 mm, and the supersaturated silicic acid solution was continuously injected into the column. Here, the supersaturated silicic acid was adjusted by mixing with distilled water of pH 8 just before the solution was injected into the column. In the results, the supersaturated silicic acid quickly deposited in the packed column, and colloidal silicic acid was not detected at the outlet of the column. The deposition amount of supersaturated silicic acid in the column decreased with time, and became larger in the longer column. Besides, the flow rate decreased with the deposition of supersaturated silicic acid. Thus, this study monitored the decrease rate of permeability with the supply amount of silicic acid. In the results, the change rate did not depend on packed length. This suggested that even with a short packed length, by considering the amount of precipitation of supersaturated silicic acid, it is possible to estimate the change in permeability similarly to the case of a long packed length. Such a decrease effect in permeability may contribute to retarding the migration of radionuclides around the repository. (authors)