在沸水式反應器中，主要作為組件的材料為不鏽鋼，在經過多年運轉後開始產生了沿晶應力腐蝕(Intergranular Stress Corrosion Cracking, IGSCC)的情況。組件的劣化不僅嚴重影響運轉安全，也提高了修復工程的耗費，為解決壓力槽內部組件的劣化情形，各國研究機構無不投入極大心力進行組件防蝕的研究。沸水式反應器在運轉時，爐心水中溶氧量約為200至400ppb，並且因為水的輻射分解效應而有過氧化氫產生，而高氧化性環境是造成IGSCC的主要環境因素，若採加氫水化學降低溶氧量，將可有效降低金屬組件的電化學腐蝕電位，降低發生IGSCC的風險。
本實驗為模擬沸水式反應器於啟動及停機過程的溫度及水化學條件，針對304不鏽鋼、304L不鏽鋼與316L不鏽鋼試片進行電化學量測，測試在這些材料在這些高溫純水環境中應力腐蝕劣化的敏感性，並探討起動階段加氫水化學之影響。

As the boiling water reactors (BWRs) age, incidents of intergranular stress corrosion cracking (IGSCC) are more readily seen in the vessel internals. To mitigate the problem of stress corrosion cracking (SCC) in the structural components, the technology of hydrogen water chemistry (HWC) has been widely adopted in BWRs around the world. The principle of HWC is to reduce the oxidizing power of the BWR coolant environment by injecting hydrogen into feedwater to recombine H2 with O2 or hydrogen peroxide (H2O2) under radiative environment. The recombination can decrease the concentration of the oxidants subsequently to lower the susceptibility of stainless steel components to SCC. As reactor startup begins, the Electrochemical Potential (ECP) is initially high in the oxygenated water environment established during a cold shutdown. Consequently, the components would show higher crack initiation and propagation rates of IGSCC during startup period than other periods of the cycle. Therefore, HWC during startup was applied and tested to demonstrate the suppression of SCC initiation.
For a safer operation of a new BWR, predicted water chemistry in the primary coolant circuit and corrosion behavior of structural materials in the BWR will be presented. The outcome would assist the reactor engineers in the design and the optimal operation of these types of reactors, ensuring nuclear safety in a proactive manner.
In this study, The corrosion potentials and corrosion current densities of 304 SS、304L SS and 316L SS will be tested in pure water at three different temperatures (200℃、250℃、288℃) with different dissolved oxygen, hydrogen peroxide or hydrogen concentrations. The results reveal that the corrosion potentials of these specimens in same water chemistry decrease while most of the current densities increase along with the increasing temperature. The outcomes also indicate the importance of adding hydrogen into feedwater while startup.

目錄
摘要 1
Abstract 2
致謝 4
目錄 6
圖目錄 8
表目錄 12
第一章 前言 14
1.1 研究背景 14
1.2 研究目的 15
第二章 基礎理論 18
2.1 混合電位理論 18
2.1.1 混合電位模式(Mixed Potential Model, MPM) 18
2.1.2 影響ECP大小的重要參數 21
2.3 伊凡斯圖(Evan’s Diagram) 22
2.3.1 伊凡斯圖 22
2.3.2 塔佛外插法(Tafel Extrapolation) 23
2.3.3 加氫水化學(HWC) 24
第三章 文獻回顧 26
3.1 應力腐蝕龜裂 26
3.1.1 材料龜裂肇因 27
3.1.2 應力腐蝕龜裂現代理論 29
3.1.3 應力腐蝕龜裂與電化學腐蝕電位關係 32
3.1.4 防治方法 35
3.1.5 應力腐蝕龜裂與沸水式反應器起爐過程 39
3.2 不鏽鋼於高溫水環境下的氧化模型態 41
3.2.1 高溫純水中不鏽鋼表面氧化層結構 42
3.2.2 雷射拉曼散射光譜分析 56
3.2.3 電化學阻抗分析 58
3.2.4 氧化膜結構對腐蝕電位的影響 60
第四章 研究方法 63
4.1 實驗方法與流程概述 63
4.2 試片準備 64
4.3 敏化程度分析 65
4.4 模擬BWR環境之水循環系統 67
4.5 參考電極製作 69
4.6 表面分析 71
4.7 高溫電化學分析 72
第五章 實驗結果 75
5.1 敏化程度 75
5.2 掃描式電子顯微鏡與雷射拉曼散射光譜結果 78
5.2.1 304不鏽鋼表面分析 80
5.2.2 304L不鏽鋼表面分析 84
5.2.3 316L不鏽鋼表面分析 89
5.3 高溫電化學分析 93
5.3.1 304不鏽鋼動態電位極化掃描 94
5.3.2 304L不鏽鋼動態電位極化掃描 101
5.3.3 316L不鏽鋼動態電位極化掃描 108
第六章 結論 118
第七章 未來工作 120
參考文獻 121

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