Transport Behavior of U-238 and Tc-99 for Radioactive Waste Repository Site

Abstract

A radioactive waste repository has been operated to store the low- and intermediate-level radioactive wastes at Wolsong site, South Korea. The second stage repository is planned to build in shallow depth condition at the same Wolsong area. Released radionuclide from the radioactive waste repository can transport through groundwater flow and affect to human health and environment. When the radionuclide is released from the repository, mobility of radionuclide is controlled by sorption and diffusion under various physical-chemical environment conditions. More researches need to increase our understanding of radionuclides (especially U-238 and Tc-99) transport behavior with various environmental conditions in the proposed second stage repository at Wolsong site, more research about mobility of radionuclide is required. Sandstone, fractured sandstone, and mudstone were collected from Wolsong site, and used for site specific investigation of radionuclide’s transport and sorption behavior. Groundwater was also obtained from Wolsong area (borehole #PW5). Batch sorption experiments, diffusion experiments, and flow through column experiments were conducted for understanding of radionuclides transport. Mobility of U-238 is highly retarded by sorption on most of three rock samples in Wolsong site, which shows the highest U-238 retardation of U-238 on fractured sandstone. The mudstone, which is major rock of Wolsong site is also relatively effective to retard Tc-99 transport because of high organic carbon content in mudstone. Therefore, the second stage of low/intermediate level radioactive waste repository in Wolsong site is considered to be effective for retardation of Tc-99 and U-238.