| Summary: | 碩士 === 國立中央大學 === 水文與海洋科學研究所 === 107 === The purpose of this study was to simulate the evolution of low-level radioactive waste placed in a near-shore tunnel disposal environment. The HYDROGEOCHEM_5.6 model was used in the study. Three different resolution grids are designed for far-field, disposal facilities and disposal tunnels, covering the material properties of multiple engineering barriers and natural barriers. The simulation is divided into a flow field simulation and a nuclear transmission simulation and is merged through boundary condition settings.
Flow field simulation results show that far-field flow field trends are related to terrain. The main flow direction from the western mountainous area to the east sea area. Far-field groundwater velocities were three-order larger than those observed in both near-field tunnels and facilities due to the hydrogeological characteristics. The flow velocity at the top and bottom of the near-field disposal tunnel is faster due to the low hydraulic conductivity of Bentonite. Type A wastes disposal tunnel flow rate is slightly higher than types B/C wastes disposal tunnel. Nuclear transport simulation results show that diffusion is the main departure method for disposal tunnel of nuclide. Types B/C wastes disposal tunnels are more effective in delaying radionuclide than type A wastes disposal tunnels. The main direction of far-field nuclear species migration is downstream from disposal facilities. High concentration values appear in the downstream nearshore area. The direction of concentration movement is slightly to the left from west to east. The long half-life nuclear concentration curve is less affected by the distance, and the peak of the short half-life nuclear concentration curve decreases with increasing distance. According to the result 59Ni, 14C, and 99Tc were major released radionuclides.
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