The first low- and intermediate-level waste (LILW) disposal facility is under construction in saturated granite in Korea. The safety assessment report (SAR) identified that different gases, such as hydrogen, carbon dioxide, and methane are generated at the disposal facility due to the corrosion of metal wastes and steel drum, and microbial degradation of organic matters. Reinforced concrete plays a role as an engineered barrier at the disposal facility, so its properties with regard to gas migration were evaluated in laboratory-scale experiments. Then modeling of gas migration was carried out to evaluate gas pressure build-up in the disposal facility.
The gas entry pressure and relative gas permeability of the concrete was determined to be 0.97±0.15 bar, and the relative gas permeability decreased exponentially with increasing water content.
The results of the modeling showed that most of hydrogen gas was dissolved in groundwater and did not significantly influence pressure build-up inside the disposal facility based on the reference case of gas generation.
Numerical modeling of gas migration at a proposed repository for low and intermediate level nuclear wastes at Oberbauenstock, Switzerland
