放射性廢棄物的處置，是所有使用核能科技的國家，都必須面對的問題，我國也是一樣。而且台灣地區土地不大、人口眾多，加上社會接受度不佳，使得放射性廢棄物的處置問題，越來越急迫。本文首先對處置概念作介紹，接著在考量各層面的因素後，對我國的處置方式提出學術上的建議。這個適合我國的處置方式為山區坑道處置。

核種的外釋情節中，最重要的媒介為地下水，而且水流快慢直接影響到遷移速率。然而隨著深度的不同，在地表下可以分成兩層。地下水面以下的飽和層，孔隙間皆充滿水，水流速較慢；地下水面以上的不飽和層，孔隙間留有空氣，但是水流速較快。本文研究發現，雖然不飽和層水流速較快，但因為存有空氣，反而不易傳輸，因此處置場應選在不飽和層。

接著想探討低放射性廢棄物中核種的傳輸行為。首先，參考文獻建立一個坑道處置場模型，根據我國預估的低放射性廢料桶總量，決定坑道的數量。然後選擇了具代表性的90Sr、137Cs及60Co為模擬對象。收集我國相關的地質水文資料作傳輸模擬。結果顯示，90Sr為遷移最遠的核種，137Cs略小，60Co的半衰期最短，故外釋距離不大。

本文使用FEHM模擬，係採用有限元素法為設計基礎的一套軟體。已在世界上應用多次，對於地下水流、溶質傳輸等模擬，具備良好的準確度。

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