Sensitivity analysis on gas migration in underground repository system for TRU waste

Tanai, Kenji ; Yamamoto, Mikihiko*; Seki, Yoshitaka*

In underground repositories for radioactive waste, significant quantities of gases may be generated as a result of metal corrosion. These gases may migrate through the engineered barrier system and the geological barrier. The potential impact of gas generation, accumulation and migration on the performances of the various barriers such as drainage of contaminated water from the repository and/or damaging of the engineered barriers due to a gas over-pressure should be assessed. The sensitivity analysis was carried out using the modified TOUGH2 model in order to clarify the impact of any input parameters. The following facts became clear as a result of this study. For the cementitious material (waste/cementitious filler), an impact of the absolute permeability and residual pore-water saturation was large. For the buffer material, absolute permeability of gas, capillary exclusion pressure and residual pore-water saturation was large.