[en] More significant alteration of montmorillonite was estimated if the precipitation of meta-stable as opposed to stable secondary minerals was assumed in a chemical/mass-transport coupled analyses of cement/bentonite engineered barrier system for TRU-2. In general, stable secondary minerals control lower solution concentrations than meta-stable secondary minerals. This suggests that the dissolution rate of montmorillonite in the stable secondary mineral case would be higher because the saturation index (S.I.) of montmorillonite would be lower than in the meta-stable secondary mineral case. The estimation results of chemical/mass-transport coupled analyses of cement/bentonite engineered barrier system for TRU-2 report, however, showed the reversed tendency. In order to understand the reasons of this reversed tendency, chemical reaction analyses of a batch system were conducted, in which mass balance can be easily understood. The 'Sato Factor (Fs)', which shows the effect of hydroxyl ion concentration on the dissolution rate of montmorillonite, and the 'Cama Factor (Fc)', which shows the effect of chemical affinity on the dissolution rate of montmorillonite, were determined using previously calculated results. No significant difference of Fs was found between the meta-stable secondary and stable secondary minerals. However, the Fc of the meta-stable secondary minerals was higher than that of the stable secondary minerals, except for a very short initial stage of reaction. These results mean that the S.I. of montmorillonite is lower in the case of meta-stable secondary minerals, except for the very short initial period. Because the Fc is higher throughout most of the reaction period in the case of meta-stable secondary minerals, the alteration is more significant. (author)