本研究目的為模擬低放射性廢棄物於近岸坑道處置環境之演化以評估廢棄物處置之長期安全。模擬採用 HYDROGEOCHEM 5.6 數值模式，設計遠場、近場處置設施、近場處置坑道三種不同解析度網格的銜接模擬，考慮多重工程障壁與地質圈天然障壁之各種材質屬性，模擬採用穩態流場模擬搭配暫態核種衰變傳輸模擬，透過邊界條件設定銜接不同層次網格之模擬工作。 流場模擬結果顯示遠場流場趨勢受地形影響，主要流向由西方山區上游向東邊海域下游流動，遠場地下水流速高於近場處置設施與近場處置坑道三個數量級，近場處置坑道因膨潤土等低透水性材質使流場在處置坑道頂部及底部有較快流速，且A類放射性廢棄物處置坑道流速略高於B、C類廢棄物處置坑道。核種傳輸模擬結果，擴散作用為近場處置坑道核種主要外釋機制，且B、C類廢棄物處置坑道相較於A類放射性廢棄物處置坑道有較佳核種遲滯效能，遠場核種遷移主要方向由處置設施向下游遷移，59Ni、14C、99Tc 為主要外釋核種，受流場方向影響，核種在處置設施下游近岸區域有較高濃度，移動方向為由上游向下游微偏北側，長半化期核種因半化期較長濃度曲線變化較不受距處置設施遠近影響，而短半化期核種濃度差異則隨遠離處置設施降低。 ;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.
