放射性廃棄物地中処分の安全性の評価に関する研究 (II)

放射性陽イオンの交換吸着体への分配におよぼす地下水中陽イオンの影響

抄録

The adsorption of radioactive cations to clay minerals, which governs the movement of radioactive cations through the saturated zone, has been investigated.
The ion exchange capacities of Amberlite IR-120B, Green Sand and KUR Sand were measured for NH₄⁺, Ca²⁺, Mg²⁺, Na⁺ and Cs^-. The results showed that the capacities of these ion exchangers were not changed with the kinds of cations examined. The distribution coefficients (Kd_A for x) of each radioactive cation (²²Na, ¹³⁷Cs, ⁵⁴Mn, ⁶⁰Co, ⁶⁵Zn, ⁸⁵Sr and ¹³³Ba) to the ion exchangers saturated with Ca²⁺, Mg²⁺ or Na⁺ were obtained for the several concentrations (Cx) of the corresponding cations. The following empirical equation was derived from the above results.
Kd_A for x=mx (Cx)^-nx
Influence of the presence of Ca²⁺, Mg²⁺ and Na⁺ were discussed using the values of mx and nx.
It can be concluded that Ca²⁺ and Mg²⁺ influence largely on the adsorption of radioactive cationsin the saturated zone.