Transport of contaminants in geologic media: Radioactive waste in salt, corrosion of copper, and colloid migration

Analytical and numerical models on mass transfer of radionuclides from a waste package to surrounding rock are analyzed. Based on developed models corresponding computer programs are developed. These models would be used to evaluate possible hazardous radionuclide release rates into the surrounding rock/biosphere. Specifically the following fields are studied. (1) Analysis on the possible copper canister pitting corrosion by sulfide intrusion is performed to predict the canister lifetime. The study includes both steady-state and time-dependent cases. (2) Analysis on the brine migration in a salt repository is studied. Brine was traditionally thought to be the major factor on radionuclide migration in salt. But results given in this dissertation provide that the brine migration velocity is small enough to be neglected. Two analyses are developed for open bore hole as well as consolidated salt cases. (3) Analysis on the radionuclide migration in a salt repository is carried out. After proving that the diffusion is a dominant migration mechanism, the time-dependent diffusive mass transfer theory is used to predict fractional release rates of low-soluble as well as highly-soluble nuclides. Also the steady-state radionuclide migration through interbeds is analyzed based on the potential flow theory. Finally assuming no advective flow inside interbeds the transient radionuclide migration into interbeds is studied. Results show that salt is a good host rock for a future high-level waste repository. (4) Analysis on the radiocolloid migration through the porous media with filtration effect is performed. Results show that due to the strong filtration radiocolloid would not migrate significant distance in geologic media. Cylindrical geometry is used. For this analysis due to the complexity of the prescribed problem the numerical analysis based on upwind scheme is developed. (5) Analysis on the radiocolloid migration through fractures with solute matrix diffusion into surrounding rock matrix is studied with and without filtration. Interaction between colloid and solute accelerates the radiocolloid migration in fractures.