白金被覆的304L不銹鋼在沸水式反應器起動過程中的腐蝕行為

Corrosion Behaviour of Platinum Treated Type 304L Stainless Steels during Simulated BWR Startup Conditions

陳岳泰(Yue-Tai Chen) ； 葉宗洸(Tsung-Kuang Yeh) ； 王美雅(Mei-Ya Wang)

《防蝕工程》 33卷2期 (2019/06) Pp. 1-12

https://doi.org/10.6376/JCCE.201906_33(2).0001

摘要

低濃度注氫及貴重金屬化學添加（NobleChem^(TM)）或線上貴重金屬化學添加（On-line NobleChem^(TM)）被廣泛應用於沸水式核反應器的結構組件上。貴重金屬藉由飼水注入後沉積於不銹鋼的結構組件表面，可以有效催化金屬表面氫氣與氧氣、過氧化氫的結合，因而降低材料表面的電化學腐蝕電位（Electrochemical Corrosion Potential, ECP），可有效抑制不銹鋼組件應力腐蝕龜裂（Stress Corrosion Cracking, SCC）的裂縫起始與成長。但根據過去的研究顯示，在反應器啟動過程中，爐水因缺乏氫氣的添加而呈現高氧化性的水環境，此時存在貴重金屬沉積的金屬表面電化學腐蝕電位會相較於未沉積的高，較高的ECP會使得金屬表面交換電流密度增加，對SCC的抑制造成反效果。本篇研究將利用慢應變速率拉伸法探討304L不銹鋼在有貴重金屬鉑被覆時，於模擬反應器啟動過程中，不同溫度下的氧化性水環境對應力腐蝕龜裂的裂縫起始影響。研究結果顯示，氧化性的水環境下具貴重金屬被覆的304L不銹鋼表面將誘發較多的SCC啟始。

關鍵字

沸水式反應器 ； 應力腐蝕龜裂 ； 貴重金屬化學添加 ； 加氫水化學 ； 慢應變速率拉伸試驗

並列摘要

Low HWC combined with noble metal chemical addition (NMCA) or Online NobleChem^(TM) (OLNC) has been adopted for boiling water reactors (BWRs) to mitigate stress corrosion cracking (SCC) by lowering the electrochemical corrosion potential (ECP) of structural materials in BWRs. Noble metal was injected into feedwater and then deposited on inner surface of the stainless steel (SS) piping to catalyze the recombination of hydrogen with oxygen and hydrogen peroxide. When the ECP was decreased to a critical potential (-230 mVSHE), the susceptibility of SCC and the crack growth rate were obviously reduced. However, some research indicated that the ECP of SS with NMCA application was increased, even higher than that without NMCA when the materials were exposed to oxidizing environments without hydrogen injection during startup of BWRs. Additionally, a higher ECP might increase the exchange current density and be detrimental to the resistance of SCC. In this study, the SCC initiation behavior of 304L SS with NMCA application was investigated in oxidizing environment with different temperature to simulate BWR water environments during startup. The results revealed that the NMCA certainly induced more crack initiation site on 304L SS in oxidizing conditions.

並列關鍵字

BWR ； Noble Metal Chemical Addition ； On-Line Noble Metal Chemical Addition ； Stress Corrosion Cracking ； Slow Strain Rate Test ； Startup