联氨对蒸汽发生器湿保养效果的影响机制研究

Research on the Influence Mechanism of Hydrazine on Steam Generator Wet Lay-up

采用氧含量测试、腐蚀形貌观察和电化学法,在模拟压水堆核电站蒸汽发生器湿保养水化学工况下,开展联氨的除氧效果对比和对典型金属材料的腐蚀风险评估。联氨的除氧效果在低浓度下(<75mg/kg)无明显差异,在150mg/kg时略有提升。试片在低浓度(≤50mg/kg)联氨溶液浸泡后表面有大量球状腐蚀产物堆积,联氨浓度提高至75mg/kg时,试片表面腐蚀产物显著减少。联氨通过在金属表面吸附并形成钝化膜,阻碍氧化还原反应的电荷转移过程,增大金属在溶液中发生电化学腐蚀的动力学阻力,从而降低腐蚀。随着联氨浓度增加,所形成的钝化膜均匀性增强,膜层厚度增大。

The oxygen content test,corrosion morphology observation and electrochemical method were used to compare the deoxidization effect and assess the corrosion risk of typical metal materials of hydrazine under the simulated water chemical condition of SG in PWR nuclear power plant during wet lay-up.The deoxygenation effect of hydrazine is not significantly different at low concentration(<75mg/kg),but slightly increases at 150mg/kg.A large number of spherical corrosion products accumulate on the surface of the test piece after immersion in hydrazine solution of low concentration(≤50mg/kg).There is a significant reduction of corrosion product when the concentration of hydrazine increases to 75mg/kg.Hydrazine forms a passivefilm by the adsorption on the metal surface,hinders the charge transfer process of redox reaction,and increases the dynamic resistance of electrochemical corrosion of metal in solution,thus reducing corrosion.With the increase of hydrazine concentration,the uniformity and thickness of the passivefilm are enhanced.