放射性廃棄物処分における緩衝材のイライト化変質シミュレーション
1994 年 34 巻 3 号 p. 149-156
詳細
1994 年 34 巻 3 号 p. 149-156
Bentonite is considered to be the most promising buffer material for radioacive waste disposal. Many of the desirable properties that bentonite has as a buffer material are attributable to the properties of smectite which is the main ingredient of bentonite. Therefore, it is important to assess the alteration of smectite in assessing the long-term stability of bentonite. Smectite is well known to be altered into illite (illitization) by natural diagenesis and hydrothermal reactions. Since the illitization deteriorates the buffer performance like low water permeability, swelling properties and radionuclides adsorption properties, the potential for the illitization of smectite in disposal environments was assessed considering the changes of temperature in buffer material with time.
The analyses of illitization were based on the rate equations of illitization derived from laboratory experiments and field observations. The analytical results show that the illitization rate is very slow except right after the burial of waste. Therefore, it is expected the long term stability of bentonite by adjusting the disposal density of wastes. This results suggest the possibility of more compact setting of wastes in the repository.
