壓水式反應器二次側結構組件腐蝕劣化的防蝕研究

Corrosion Mitigation of Structural Materials in the Secondary Cooling System of Pressurized Water Reactors

壓水式反應器二次側結構組件的腐蝕情況以蒸氣產生器最為嚴重，因為在蒸氣產生器內的管件與支撐用的管板之間會有縫隙產生，容易導致間隙腐蝕。此外，腐蝕產物堆積在縫隙硬化後會擠壓管件造成凹陷，在管件U型彎曲部分存在張應力，容易出現應力腐蝕破裂。
目前核三廠使用聯胺（Hydrazine）和乙醇胺（Ethanolamine, ETA）作為水質控制的添加劑，蒸氣產生器的酸鹼值約控制在9.6，聯胺添加濃度約為30 parts per billion （ppb），乙醇胺濃度約為1 ppb，其他雜質濃度都維持在接近偵測極限。
因此，實驗設計為透過壓水式反應器二次側水循環模擬迴路，針對600合金和690合金試片進行均勻腐蝕試驗、U-bend應力腐蝕試驗、間隙腐蝕試驗和CBB （Crevice Bent Beam）腐蝕試驗。

Steam generators show the most severe condition of the corrosion in PWR secondary side because there are crevices between the tube bundles and support tube sheet, it may cause crevice corrosion in the intermediate gap. The accumulated sludge in the gap will gradually harden, it will press the tubes to cause denting.
Maanshan Nuclear Power Plant utilizes hydrazine and ethanolamine to control water quality. The pH value in steam generator blow down is around 9.6 at 25℃. The concentration of hydrazine and ethanolamine are 30 ppb and 1 ppb respectively. Other impurity concentrations are quite low to near detection limit.
Therefore, the designation of the experiment will test Inconel 600 alloy and Inconel 690 alloy in simulated PWR secondary side water chemistry circuit through different sample conditions and different water chemistry conditions.