相較於其他能源，核能提供了較無污染的乾淨能源，但也必須承擔核電廠運轉過程所產生的高階廢棄物的處置問題。然而，在興建高階廢棄物處置設施時產生的力學應力效應與高階廢棄物產生熱與輻射的效應可能會出現裂隙。這些裂隙會是放射性核種透過地下水外釋到生物圈主要的通道，且在裂隙中地下水常存在膠體。可移動膠體可吸附放射性核種並加速其傳輸。因此更真實了解放射性核種在裂隙-母岩系統的遷移行為對於高階廢棄物場址各階段的安全評估都相當重要。本研究發展出一個數值模式來模擬膠體與放射性核種衰變鏈多成員核種在裂隙-母岩系統中的傳輸。本模式採用的是使用有限差分法獲得的數值解，並撰寫成FORTRAN程式執行數值模式的計算。結果表明膠體會加速放射性核種衰變鏈多成員核種傳輸。接著用來探討膠體濃度的時間與空間變化對放射性核種衰變鏈多成員核種傳輸的影響，發現在250年前若沒考慮膠體濃度的時間與空間變化將會高估放射性核種衰變鏈多成員核種的傳輸。此外，模型也用於計算高階廢棄物深層地質處置場安全評估的劑量率。該模型考慮了膠體濃度的變化，將可增加高階廢棄物深層地質處置場安全評估的信賴度。;Compared with other energy sources, nuclear energy provides clean energy with less contaminant, but it also has to deal with the disposal of high-level waste (HLW) generated during the operation of nuclear power plants. However, the fractures may appear due to the mechanical stress created during the construction of deep geological disposal facilities and thermal and radiation effects due to the presence of HLW. These fractures will be the main pathway for the release of radionuclides to the biosphere through groundwater, and colloids often exist in the groundwater in the fractures. Mobile colloids can sorb radionuclides and facilitate their transport. Therefore, a more realistic understanding of the transport behavior of radionuclides in the fracture-matrix system is very important for the safety evaluation of HLW sites at all stages. In this study, a numerical model was developed to simulate the transport of multiple members of a radionuclide decay chain, and colloids in the fracture-matrix system. The numerical solution of the model was obtained using the finite difference method, and a FORTRAN computer code has been programmed for our proposed numerical solutions. The results show that colloids can facilitate the transport of multiple members of a radionuclide decay chain. Then, the effects of the temporal and spatial variation of colloid concentration on the transport of multiple members of a radionuclide decay chain were discussed, and it was found that 250 years ago, if t the temporal and spatial variation of colloid concentration were not considered, the transport of multiple members of a radionuclide decay chain would be overestimated. The developed numerical model is applied to calculate dose rate for safety assessment of HLW deep geological repositories. This model considering the change in the concentration of colloids which will increase the reliability of the safety assessment of HLW deep geological repositories.
