Development of a method of safety assessment for geological disposal considering long-term evolution of geological and topographical environment by uplift and erosion
Wakasugi, Keiichiro; Yamaguchi, Masaaki ; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko ; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*
This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.