[1D14-19] Migration in Host Rock

[1D14] Analytical study of the effect of borehole on nuclide migration

*Takuma Sawaguchi¹, Shizuka Takai¹, Emiko Uchikoshi², Seiji Takeda¹ (1. JAEA, 2. NAIS)

Keywords:Borehole, Closure confirmation, Intermediate depth disposal, Groundwater flow analysis

For the intermediate depth disposal, it is necessary to confirm that the monitoring borehole is properly backfilled. In this study, groundwater flow analysis was performed to understand the effect of borehole on nuclide migration under different environmental conditions and borehole settings. As a result, under conditions where the borehole was backfilled with highly permeable material, groundwater flowing tens of meters around the borehole was drawn into the borehole in the pressurized aquifer below clay-layer. However, in the unpressurized aquifer without clay-layer, only groundwater near the borehole was drawn. These results indicate that while measures to reduce the groundwater drawdown are necessary in geologic structures with clay-layers, the backfilling requirements could be relaxed for unpressurized aquifers with only minor groundwater drawdown.