放射性廢料的處置一直是世界各國亟欲解決的一大問題，由於廢料體本身具有能放出游離輻射之放射性核種，因此在處理上並不如一般廢棄物那樣簡易。目前採取的最佳作法乃是利用地質處置，即在地層中設立處置場，並將廢料埋在其中，以天然地質岩層以及人工障壁構成一個多重障壁系統，來減緩放射性核種釋出的濃度和時間。
本論文主要是以一島嶼海床處置場為主體，初步模擬核種在此一處置場穿過水泥工程障壁的傳輸機制與行為，藉以探討建構處置場的水泥工程障壁存在之重要性與功用；並探討水泥工程障壁之劣化對核種釋出傳輸所造成之影響，希望能提供將來國內可能規劃設立於小坵嶼內的低放射性廢料處置場之參考模式。

本文中首先將水泥工程障壁視為一多孔性介質，分別假設在其不會產生劣化以及完全劣化之情形下對核種傳輸之影響，並針對參數進行討論。結果可發現當工程障壁完全劣化，視同地質母岩性質時，對於廢料體所釋出的核種幾乎沒有侷限力，釋出之核種濃度也較無劣化產生之狀況高出許多，由此可突顯出水泥障壁存在之重要性。接著假設水泥障壁開始劣化時會產生裂縫，且裂縫數隨著時間增加，其型式視為多重平行裂縫之模式，針對重要參數進行討論；又假設兩種函數：線性及曲線函數，來模擬裂縫間距和重要參數的變化，藉此討論工程障壁之劣化狀況。由結果顯示以線性函數劣化之工程障壁對核種釋出量比曲線函數劣化時來得高，釋出時間也較早。因本文中使用之兩函數為假設的參考函數，故對水泥工程障壁的實際劣化模式應加以研究討論。

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