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Kim J.-W.,Korea Atomic Energy Research Institute | Baik M.-H.,Korea Atomic Energy Research Institute | Jung H.,Korea Radioactive waste Management Corporation KRMC | Jeong J.-T.,Korea Atomic Energy Research Institute
Journal of Contaminant Hydrology | Year: 2013

A numerical model for the reactive transport of uranium and bacteria in fractured rock was newly developed. The conceptual model consists of four phases (fracture, fracture surface, matrix pore, and matrix solid) and eight constituents (solutes in the fracture, on the fracture surface, on mobile bacteria, on immobile bacteria, in the rock matrix pores and on the rock matrix solids, and bacteria in the fracture and on the fracture surface). In addition to the kinetic sorption/desorption of uranium and bacteria, uranium reduction reaction accompanying with bacteria growth was considered in the reactive transport. The non-linear reactive transport equations were numerically solved using the symmetric sequential iterative scheme of the operator-splitting method. The transport and kinetic reaction modules in the developed model were separately verified, and the results were reasonably acceptable. From the sensitivity analysis, the uranium transport was generally more sensitive to the sorption rate rather than desorption rate of U(VI). Considering a uranium reduction reaction, bacteria could considerably retard the uranium transport no matter the uranium sorption/desorption rates. As the affinity of U(VI) onto the bacteria becomes higher than that onto a rock fracture surface, a biofilm effect, rather than a colloidal effect, of the bacteria becomes more influential on the uranium transport. © 2013 Elsevier B.V. Source


Jung H.,Korea Radioactive waste Management Corporation KRMC | Kwon K.-J.,Korea Radioactive waste Management Corporation KRMC | Lee E.,Korea Radioactive waste Management Corporation KRMC | Kim D.-G.,Korea Institute of Construction Technology | Kim G.Y.,Korea Atomic Energy Research Institute
Corrosion Engineering Science and Technology | Year: 2011

A series of electrochemical experiments were conducted to investigate the effect of dissolved oxygen, pH and Cl̄ on the corrosion rate of reinforcing steel of geological disposal facility saturated with groundwater. It was found that the corrosion rate was proportional to the concentration of Cl̄ and dissolved oxygen which are known as a corrosive agent and an electron acceptor, respectively. The pH level also strongly influenced the corrosion rate of the reinforcing steel. Under the pore water conditions of concrete structure of geological disposal facility, i.e. pH of 10-12 and dissolved oxygen of 1 mg L-1, the corrosion rate of reinforcing steel was determined to be in the range of ̃10-8 to ̃10-9 m/year. The corrosion rates were higher than those estimated from an empirical model based on the diffusion of dissolved oxygen. © 2011 Institute of Materials, Minerals and Mining. Source


Lee E.,Korea Radioactive waste Management Corporation KRMC | Jung H.,Korea Radioactive waste Management Corporation KRMC | Kwon K.-J.,Korea Radioactive waste Management Corporation KRMC | Kim D.-G.,Korea Institute of Construction Technology
Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation, ICEM | Year: 2010

Laboratory-scale experiments were performed to understand the porosity change of cement pastes. The cement pastes were prepared using commercially available Type-I ordinary Portland cement (OPC). As the cement pastes were exposed in water, the porosity of the cement pastes sharply increased; however, the slow decrease of porosity was observed as the dissolution period was extended more than 50 days. As expected, the dissolution reaction was significantly influenced by w/c raito and the ionic strength of solution. A thermodynamic model was applied to simulate the porosity change of the cement pastes. It was highly influenced by the depth of the cement pastes. There was porosity increase on the surface of the cement pastes due to dissolution of hydration products, such as portlandite, ettringite, and CSH. However, the decrease of porosity was estimated inside the cement pastes due to the precipitation of cement minerals. © 2010 by ASME. Source


Ha J.-C.,Korea Radioactive waste Management Corporation KRMC | Lee J.-H.,Korea Radioactive waste Management Corporation KRMC | Jung H.,Korea Radioactive waste Management Corporation KRMC | Kim J.,FNC Technology
Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation, ICEM | Year: 2013

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. Copyright © 2013 by ASME. Source

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