Evaluation of pH Control Agents Influencing on Corrosion of Carbon Steel in Secondary Water Chemistry Condition of Pressurized Water Reactor

摘要

Effect of various pH agents on the corrosion behavior of carbon steel was investigated under a simulated secondary water chemistry condition of pressurized water reactor (PWR) at laboratory, and its performances was compared with the field data tested at Uljin NPP unit 2 reactor. All tests were carried out at temperatures of 50°C - 250°C and pHs of 8.5 - 10, and the pH at a given temperature was controlled by adding different agents and additive concentrations. Laboratory data indicated that the corrosion rate of carbon steel decreased as the pH increased under the test conditions and the highest corrosion rate was measured at 150°C. This high corrosion rate may be related to high dissolution and instability of Fe oxide (Fe_3O_4) at 150°C. It is also found that an addition of ethanolamine (ETA) to ammonia was more effective than ammonia alone, and clearly demonstrated more than 50% of iron reduction at pHs of 9.5 or higher, especially in the steam generator (SG) and the moisture separator & re-heater (MSR).