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对压水堆核电站(PWR)常用的316LN不锈钢模拟压水堆一回路条件下,进行加锌浓度为10 ppb和50 ppb的堆外高温动水回路腐蚀实验。实验1 200 h后,对316LN不锈钢表面氧化膜进行腐蚀失重分析,采用SEM-EDS观察氧化膜表面形貌和元素分布,XPS进行元素深度分布分析,GIXRD分析氧化膜结构。分析发现,加锌50 ppb样品比加锌10 ppb样品表面形成的氧化膜颗粒更细小,与基体结合更紧密,氧化膜厚度明显减薄,氧化膜晶粒尺寸分布均服从高斯函数规律。加锌后,在氧化膜中形成了更稳定的ZnCr2O4和ZnFe2O4化合物,使得氧化膜处于低能量状态,从而更加稳定,具有更好的保护性。
Corrosion tests on 10kV and 50ppb Zn-added hydrothermal circuits were carried out for the primary circuit of 316LN stainless steel simulated PWR, which is commonly used in pressurized water reactor nuclear power plants (PWRs). After 200 h of experiment, the corrosion loss of 316LN stainless steel oxide film was observed. The surface morphology and elemental distribution of oxide film were observed by SEM-EDS. The elemental depth distribution was analyzed by XPS. The oxide film structure was analyzed by GIXRD. It is found that the oxide film formed on the 50 ppb zinc-added sample is finer than that on the zinc-added 10 ppb sample, and the oxide film is more tightly bonded to the substrate. The oxide film thickness is significantly reduced, and the grain size distribution of the oxide film obeys the Gaussian function law. After adding zinc, more stable ZnCr2O4 and ZnFe2O4 compounds are formed in the oxide film, so that the oxide film is in a low energy state, thereby being more stable and having better protection.