當核電廠達到可以除役的年限，而且不再延役時，將會進入除役階段。核電廠除役過程中，金屬組件上經由除污程序移除表面受到活化的氧化層與基材表層後達可外釋標準，金屬組件就可做為一般金屬廢棄物回收，減少金屬放射性廢棄物的量。
本研究將針對常作為核一廠組件之304不銹鋼與銲材之82合金進行除污研究。本研究的除污方法選擇電化學除污法進行探討，原因為電化學除污對導電材料具有相當高除污因子，可有效地去除導體表面的放射性污染物直至外釋標準，且電化學除污產生的二次廢棄物少於化學除污。
本研究共分為兩個部分，第一部分為透過高溫爐管與電鍍法分別模擬核電廠金屬組件的氧化層。為了探討除污速率與機制，針對四種類型的試片進行備製，包含基材、高溫處理氧化層、電鍍氧化層、複合氧化層，並利用掃描式電子顯微鏡、Ｘ光繞射與拉曼光譜，分析氧化層的結構與厚度。第二部分為電化學除污對於氧化層與金屬基材去除的效果，量測每次電解前後重量與厚度的變化，比較40wt%與60wt%磷酸濃度對金屬組件除污的影響，以及在40wt%磷酸濃度下，異材銲件除污效果。
模擬氧化層的結果顯示，304不銹鋼經過高溫氧化處理，主要氧化層為FeCr2O4，再透過電鍍沉積 Fe3O4模擬crud來形成複合氧化層。在異材銲件的部份，82合金經過高溫氧化處理後，會生成Cr2O3、FeCr2O4與NiFe2O4混合氧化層，再透過電鍍沉積 Fe3O4形成複合氧化層。
電化學除污的結果顯示，在304不銹鋼的部分，以40wt%磷酸水溶液去除FeCr2O4氧化層之蝕刻速率優於60wt%，而60wt%磷酸水溶液去除Fe4O3氧化層與304不銹鋼基材之蝕刻速率優於40wt%。在異材銲件的部份，銲材之82合金蝕刻造成的厚度變化是母材之304不銹鋼的兩倍以上，但82合金表面之複合氧化層在30 ℃的40wt%磷酸濃度下，蝕刻後局部區域出現氧化層殘留，然而溫度升高至60 ℃，氧化層殘留的問題可獲得改善。

When a nuclear power plant has reached the end of its operational life and has not extended the service, it enters the stage of decommissioning. After the decontamination process, the surface of the metal component and its oxide layer were removed. Subsequently, the metal components can be recycled as the general metal waste. Furthermore, the decontamination process can reduce the amount of radioactive materials.
Austenitic 304 SS and alloy 82 are extensively used in Chinshan nuclear plant. Therefore 304 SS and 304 SS-alloy 82 dissimilar metal weld were studied in this experiment. This research is focus on electrochemical decontamination. Because electrochemical decontamination has a relatively high decontamination factor for conductive materials and this method produces less secondary waste than chemical decontamination.
This study of 304 stainless steel is divided into two parts. The first part is to simulate the oxide layer of metal components of nuclear power plants through the furnace and electrodeposition method, respectively. In order to discuss the rate of decontamination and mechanism in detail, the samples were divided into four types: base material, high temperature treated oxide layer with the base metal, electrodeposited oxide layer with the base metal, and multiple oxide layer. The morphology, thickness and structure of oxide was analysed by SEM, XRD and Raman spectroscopy. The second part is the effect of electrochemical decontamination on the removal of oxide layer and metal substrate. The effect of 40wt% and 60wt% phosphoric acid concentration on the decontamination of metal components were compared by measuring the change weight and thickness before and after each electrolysis. At 40wt% phosphoric acid concentration, the decontamination effect of dissimilar metal welds also be discussed.
The results of the simulated oxide layer show that the main oxide layer on the 304 stainless steel is FeCr2O4 after high temperature oxidation treatment. After that, Electrodeposited Fe3O4 simulates crud to form a multiple oxide layer. In the parts of dissimilar matal welds, the oxide layer on the alloy 82 is a mixed oxide layer of Cr2O3, FeCr2O4 and NiFe2O4 after high temperature oxidation treatment. Next, electrodeposited Fe3O4 simulates crud to form a multiple oxide layer.
The results of electrochemical decontamination show that in the part of 304 stainless steel, the etching rate of the FeCr2O4 oxide layer with a 40wt% phosphoric acid aqueous solution is better than 60wt%, and the etching rate of the 60wt% phosphoric acid aqueous solution to remove the Fe4O3 oxide layer and the 304 stainless steel substrate is better than 40wt%. In the part of 304SS-alloy 82 dissimilar metal weld component, thickness change which was caused by etching to alloy 82 (solder) is more than twice as fast as is 304 stainless steel (parent metal). The oxide layer remains on local surface after etching the multiple oxide layer on the surface of alloy 82 under the condition of 40wt% phosphate concentration at 30°C. However, the temperature rises to 60°C, the problem of remaining oxide layer was improved.

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