目前，高階放射性廢棄物的處置主要是使用深地層處置法。深地層處置法的概念是以人工障壁和天然障壁組成的多重屏障。緩衝區屬於人工障壁的一部份，其介於廢料罐和母岩間，其作用為防止地下水入侵以及核種吸附。在前人的解析解中，假設核種的擴散是只有單向。然而實際情況中，擴散是由於濃度梯度造成物質由高濃度往低濃度方向移動，因此前人僅考慮單向的假設與此不符。本研究目的是發展二維圓柱座標系統的解析解模式，此模式考慮軸對稱擴散與和核種衰變。假設核種以廢料罐為中心，以徑向擴散向外傳輸情況。與前人之解析解比較，結果顯示對於低衰變常數或是低分配係數的核種，兩種模式的濃度差較大。此外，前人模式中的通量約為本研究中模式通量的兩倍。;At present, a deep geological disposal is designed to store high-level radioactive nuclear waste. Its conception is a multi-barrier structure consisting of engineered barriers and natural barriers. The buffer zone, between the waste can and the bedrock, is a part of the engineered barriers and is to prevent groundwater infiltration and sorbing radionuclides. In previous studies, analytical solution for radionuclides transport is assumed that diffusion is in the transverse direction. However, gradient of concentration makes atoms move from high concentration to low concentration in many different directions. The purpose is to develop the analytical solution in two-dimensional cylindrical coordinate system for radionuclide transport with decay and diffusion. It is assumed that radionuclides transports are radial diffusion and move from the central of the waste can to outside. Compare to previous study, the result shows that difference in concentration between two models gradually increases with low decay constant or low distribution. Besides, the flux in previous model is about two times as that in this study model.
