沸水式反應器在1970年代如雨後春筍般大量啟用，至今已三十多年。運轉過程中陸續發現在爐心組件上產生應力腐蝕龜裂(Stress Corrosion Cracking, SCC)。原因是爐心內部的輻射分解效應，純水經由輻射分解產生過氧化氫等氧化劑，使電化學腐蝕電位(Electrochemical Corrosion Potential, ECP)上升，造成裂縫成長的驅動力上升。為了降低裂縫的成長速率，以及避免新裂縫的產生，加氫水化學被廣泛地運用在大部分的沸水式反應器中，其原理是藉由氫氣與氧氣的再結合作用，使水中易造成腐蝕的氧化劑濃度下降，以達到降低腐蝕電位，進而有效減少裂縫的起始與成長。但是過多的氫氣會造成副作用，如輻射人員劑量過高等，於是添加貴重金屬被覆配合加氫水化學的技術開始被採納，其原理是藉由貴重金屬催化氫氣與氧氣的再結合作用，在降低注氫量的同時達到低腐蝕電位。但在電廠起動過程中，上一個燃料周期殘留大量的氧化劑在爐心環境中，且大修時暴露在空氣環境，都會使爐水含有強烈的氧化性。而一般來說，氫氣並不會一起動就開始注入，而是要達到一定的功率，而根據理論，貴重金屬也會加速氧化劑的反應，於是在此狀態下是否有腐蝕的現象成為了需要討論的議題。本研究探討不同氧化膜結構之304不鏽鋼表面對於被覆白金之效率影響。不鏽鋼試片將在兩種不同的高溫水環境下預氧化，分別是100 ppb之氫氣以及100 ppb之過氧化氫。在288℃下，將白金被覆至試片表面，並在三個不同的工作溫度，測量不同水環境有無被覆白金的電化學差異。結果顯示在氧化性的水環境中，白金被覆試片的腐蝕電位及腐蝕速率皆高於未被覆的試片；但在還原性環境裡，白金則能有效的催化氫氣的反應，使得腐蝕電位及腐蝕速率都低於未被覆的試片，達到防蝕的效果。

In order to mitigate the problem of stress corrosion cracking (SCC) in the structural components, the technology of hydrogen water chemistry (HWC) or low HWC combined with noble metal chemical application (NMCA) or On-line NobleChemTM (OLNC) has been widely adopted in BWRs around the world. As reactor startup begins, the ECP is initially high in the oxygenated water environment established during a cold shutdown. The oxidizing chemistry environment of BWR reactor water is the key factor promoting IGSCC of stainless steel and nickel-based alloys in the reactor coolant system piping and vessel internals. Due to the adverse effects of HWC in elevating the operational and shutdown dose rates in a BWR, noble metals have been developed to enhance the effectiveness of HWC in lowering hydrogen consumption and expanding protection areas. Reactor components at different locations are exposed to different water chemistry conditions (e.g. O2, H2O2 and H2). As platinum was applied in the BWRs, the deposition behavior of platinum would affect the corrosion mitigation of the components.
In this study, the impact of various oxide structures of 304 stainless steel components on the efficiency of platinum deposition was established in high temperature water environments. All samples were pre-oxidized in high temperature water containing either 100 ppb hydrogen peroxide or 100 ppb dissolved hydrogen, followed by a hydrothermal deposition treatment with platinum. The platinum treating process was conducted at 288 oC for 7 days in a dynamic loop that contained pure water and 1 ppm Na2Pt(OH)6. The corrosion potentials and corrosion current densities of 304SS specimens were investigated in pure water environment at various temperatures (200, 250 and 288 oC). In addition, the specimens with Pt coating were also conducted via electrochemical polarization experiment under the same water chemistry condition.

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