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首页> 外文会议>12th International Conference on Environmental Degradation of Materials in Nuclear Power Systems: Water Reactors 2005 vol.2 >EFFECTS OF BULK WATER CHEMISTRY ON ECP DISTRIBUTION INSIDE A CREVICE
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EFFECTS OF BULK WATER CHEMISTRY ON ECP DISTRIBUTION INSIDE A CREVICE

机译：散装水化学性质对容器内ECP分布的影响

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Water chemistry of an occluded volume in a crack has been studied in order to understand the mechanisms of intergranular stress corrosion cracking (IGSCC) in a boiling water reactor (BWR) environment. Lectrochemical corrosion potential (ECP) in a crevice made in an austenite type 304 stainless steel specimen has been measured under simulated BWR conditions. The ECP distribution along the simulated crack (crevice) was affected by bulk water chemistry. When oxygen concentration was high in the bulk, the potential difference inside and outside of the crack (△E) was about 0.3V under a stagnant condition. On the other hand, when oxygen was removed from the bulk, △E was less than 0.1V. The ECP value was rather uniform and below -0.4 V vs. SHE deep in the crevice. When water flowed, oxygen passed inside the crack with the flow and the ECP just inside the crack mouth got higher. This caused the crack tip potential to have a large △E. When the ECP of the surface outside the crack was lowered by a noble metal chemical addition (NMCA) without decrease of bulk oxygen concentration, the ECP inside the crack was also low enough to mitigate IGSCC under the quiescent condition. However, when bulk water flowed, water-borne oxygen caused the ECP a the surface, untreated with noble metal, inside the crack to rise. This also caused the crack tip potential to have a large △E. Therefore, if the △E is a motivating force for crack growth, it is effective to reduce bulk oxidant concentrations such as oxygen and hydrogen peroxide in order to lower △E. Crack growth rates (CGRs) were measured to study effects of the △E caused by the flow and deep crack condition. It was confirmed that at low oxygen concentration, the CGR was sufficiently mitigated compared to the oxidizing condition and catalytically protected condition. It was concluded that lowering the bulk oxidant concentration is more essential to suppress the crack propagation than lowering the surface ECP outside the crack by surface treatment when the present crack is deeper than the catalytic protection range.
机译：为了了解沸腾水反应堆（BWR）环境中的晶间应力腐蚀开裂（IGSCC）的机理，已经研究了裂纹中的闭塞体积的水化学性质。在模拟的BWR条件下，已经测量了奥氏体304不锈钢试样中缝隙中的化学腐蚀电位（ECP）。沿模拟裂缝（缝隙）的ECP分布受整体水化学的影响。当本体中的氧浓度高时，在停滞状态下裂纹内部和外部的电位差（△E）约为0.3V。另一方面，当从主体中除去氧气时，△E小于0.1V。 ECP值相当均匀，缝隙深处的SHE低于-0.4V。当水流过时，氧气随流通过裂纹内部，而裂纹口内部的ECP升高。这导致裂纹尖端电位具有大的△E。当通过添加贵金属化学物质（NMCA）降低裂纹外部表面的ECP而不降低整体氧浓度时，裂纹内部的ECP也足够低，可以减轻静态条件下的IGSCC。但是，当大量水流过时，水性氧气导致ECP表面裂纹（未经贵金属处理）表面上升。这也导致裂纹尖端电位具有大的△E。因此，如果△E是裂纹扩展的动力，则为了降低△E，降低氧，过氧化氢等的整体氧化剂浓度是有效的。测量裂纹扩展速率（CGR）以研究流动和深裂纹条件对△E的影响。证实了在低氧浓度下，与氧化条件和催化保护条件相比，CGR被充分减轻。结论是，当当前裂纹的深度大于催化保护范围时，降低整体氧化剂浓度对于抑制裂纹扩展比通过表面处理降低裂纹外部的表面ECP更为重要。

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