對核廢料深層地質處置的安全評估工作，預測放射性核種在地質介質的遷移為一必要且重要的工作。解析解模式儘管有許多限制，但相對於數值模式需要耗費大量的計算時間，解析解模式確是模擬放射性核種長時間傳輸行為的有效工具。當放射性核種在地質環境遷移，由於真實的現地系統很少為均質而且其地質特性還會隨著空間變異，因此往往都是放射性核種的遷移經過多層非均質介質。由於不同區域有其不同的物理或化學特性，因此傳輸行為是很容易受影響而改變的，所以放射性核種的宿命會變的更為複雜。然而，相較於文獻中的大量放射性核種於均質地質介質遷移的解析解模式，，很少有解析解模式考慮多層非均質地質介質。 本研究的目的為發展預測放射性核種衰變鏈非均質層狀地質介質遷移的解析解模式，對相互耦合每一層的移流-延散聯立方程組以及其所對應的邊界條件使用Laplace轉換技巧結合序列代換求解。所發展的解析解模式將和使用Laplace轉換有限差分求解之數值解模式比較以確認解的準確性。本研究發將提出所發展解析解模式的應用範例。最後，解析解模式結合放射性輻射劑量評估模式將會是核廢料在深層地質處置安全評估的有效工具。 ;In safety evaluation of deep geologic nuclear waste repository systems, predictions of migrations of radionuclides in geological media are essential and important. Despite their limitations, analytical models are efficient tools for long-term predictions of radionuclide transport as compared to time-marching numerical models which generally put severe demands on computational time. When radionuclides migrate in the geological environment, they typically move through layered heterogeneous media because that actual field systems generally are seldom homogeneous with their properties usually spatially variable. Transport behavior is susceptible to change, and the fate of radionuclide becomes more complicated when the distinct zones have different physical and chemical properties. However, few analytical solutions for radionuclide transport in layered heterogeneous geological media have been found compared with a large body of analytical models in the literature pertaining to radionuclide transport in homogeneous geological media. The objective of this project is designed to develop a novel analytical model for predicting the long-term plume behavior of a radionuclide decay chain in layered heterogeneous geological media. The coupled transient advection-dispersion equations for each layer and their associated boundary conditions will be solved using the Laplace transform technique with the help of sequential substitutions The accuracy and robustness of the developed model is evaluated by a numerical model using a Laplace transform finite difference scheme. An application example of the derived novel analytical model will be presented. Moreover, combination of the developed analytical model with the radiological dose assessment model will be effective for safety evaluation of deep geologic nuclear waste repository systems.
