摘要
核電廠採用的抗腐蝕不□鋼，理論上應至少具有四十年的使用年限，不會因發生腐蝕而影響運轉安全。但1974年起，沸水式反應器（Boiling Water Reactor, BWR）開始出現爐心內部組件龜裂（Vessel Internal Cracking, VIC）的問題，應力腐蝕龜裂（Stress Corrosion Cracking, SCC）是造成壓力槽內部組件劣化的主因，最常發生的劣化案例為不□鋼組件的沿晶應力腐蝕龜裂（Intergranular Stress Corrosion Cracking, IGSCC），及輻射促進應力腐蝕龜裂（Irradiation-Assisted Stress Corrosion Cracking, IASCC）。對於解決服役中電廠壓力槽內部不易更換組件的腐蝕現象，核能工業多採用加氫水化學（Hydrogen Water Chemistry, HWC）技術，降低組件材料的腐蝕電位（Electrochemical Corrosion Potential, ECP），抑制SCC的發生。但HWC有大幅增加管路輻射劑量的副作用。而對於部份壓力槽內組件，如爐心上方空間和爐心側板上部等過氧化氫濃度偏高的區域，抑制IGSCC的效果也不彰。因此又有催化性被覆（Catalytic Coatings）技術（或稱貴重金屬覆膜技術）的開發，利用貴重金屬的催化性，促進HWC的效益，在低注氫量即可達到防制SCC的效果。

催化性披覆技術中以貴重金屬化學添加法（Noble Metal Chemical Addition, NMCA）為目前研發的趨勢，目前更已在服役的電廠中進行應用。應用結果證實在較少的注氫量下，NMCA即可有效的降低ECP，使其低於臨界電位 -230mV（vs. SHE）以下。

為了驗證貴重金屬的催化理論及其效益，對於溶氫濃度不足情況下(或純溶氧情況下)可能發生的副作用，必須進一步的探討和研究。本研究以電鍍處理試片(理論厚度500 Å和2000 Å)、化學添加處理試片(12小時和24小時覆膜)，以及未覆膜的試片，於模擬BWR爐水環境下(溶氧濃度為300 ppb)進行裂縫成長量測實驗，觀察不同覆膜條件試片的裂縫成長速率(Crack Growth Rate, CGR)。實驗結果顯示，貴重金屬電鍍處理試片的CGR比未覆膜試片高，IGSCC的情形比較嚴重，電鍍理論厚度越大的試片，CGR越高。NMCA覆膜時間的不同對裂縫成長速率影響看不出明顯差異。本研究另外利用上述試片，分別以除氧和通空氣的Na2B4O7待測溶液進行室溫下的動態極化掃描，結果發現鉑覆膜的試片腐蝕電位比未覆膜試片高，通空氣條件下覆膜試片的鈍化電流密度比未覆膜試片高。

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