Long-term Monitoring Results and Evaluation of Water Chemistry Parameters Related to Steam Generator for a Nuclear Power Plant

Based on the practical operating data, the trend analysis and evaluation of the long-term monitoring results of the main water chemistry parameters related to the steam generator (SG) for a nuclear power plant were carried out. The evaluation results show that since the units started to run at full power stage, the SG secondary side water quality was generally in good condition, and the annual average concentration of impurity ions (Na⁺, SO₄^2-, Cl^-) in the blow-down system of unit 1/2 decreased with operating reactor year and tended to stabilize, reaching 0.5/0.4 μg/L, 1.3/1.6 μg/L, and 0.9/0.8 μg/L respectively; the annual average concentration of Fe in the main water supply system decreased with operating reactor year and tended to stabilize, reaching 0.9/0.7 μg/L; the annual average concentration of dissolved oxygen (DO) in the main water supply system controlled below the expected value (3 μg/L), but with the increase in operating years, it showed a slow upward trend, and the increase in sludge deposition was positively correlated with the increase in dissolved oxygen content on the secondary side. The possible risk of corrosion of SG heat transfer tubes caused by very deviated water chemical conditions was evaluated. Relevant measures and suggestions were proposed for the control and optimization of water quality operating conditions that are conducive to maintaining the reliability of SG operation.