Study on the nuclide behavior in the engineered barrier for TRU waste (V)

Yanagisawa, Ichiro*; Katsurai, Kiyomichi*; Mukai, Satoru*; not registered

In this study, in-diffusion experiment was conducted under reducing condition to measure apparent diffusion coefficients and distribution coefficients of Uranium and Neptunium for bentonite materials as engineered barrier. The summary of this study is as follows: (1)Apparent diffusion coefficients of U and Np under reducing condition were one or two orders magnitude lower than those of the results obtained in the previous studies. From this result, the valence of U and Np was estimated to be +4 charge during diffusion experiment. (2)Distribution coefficients of U and Np for the system of equilibriated water with bentonite at density of 1.6 g/cm were a little lower than those for the other synthetic groundwater system. (3)Distribution coefficients of Cs and Sr decreased as ion strength of pore water in bentonite increased. Distribution coefficient of Sr increased for alternation of bentonite. (4)Distribution coefficients of Ni, Sn, Zr and Nb were little difference for any type of bentonite or synthetic groundwater. (5)Distribution coefficients or Am for Na-type of bentonite was higher than that of Ca-type of bentonite. But the difference of distribution coefficients for any synthetic groundwater was small. (6)Data base of apparent diffusion coefficients and distribution coefficients was renewed.