压水堆一回路硅酸盐沉积热力学分析
Thermodynamic Analysis of Silicate Deposition in Primary Circuit

污物在燃料棒上的沉积严重危害核电站的安全经济运行。本文运用热力学分析方法，计算了压水堆一回路Al、Ca和Mg与Si沉积形成硅酸盐的高温热力学数据，获得了553.15 K、583.15 K和613.15 K三个温度下Si-H₂O、Al-H₂O、Ca-Si-H₂O、Mg-Si-H₂O、Al-Mg-Si-H₂O和Ca-Mg-Si-H₂O六个体系的高温E-pH图，确定了高温水溶液中各固相的稳定存在区域和沉淀生成与溶解的倾向性，为完善污垢沉积模型提供参考。结果表明，在压水堆一回路正常运行条件下，只有Si-H₂O和Al-H₂O体系中以溶解态物质H₃SiO₄^-和Al(OH)4^-的形式稳定存在，其余体系均为固态物质稳定存在。随着温度升高，一回路中各体系的固相区域均有增大，说明沉淀进行生成反应的倾向性更大，也更易沉积在燃料棒上。
The deposition of crud on fuel rods seriously endangers the safe and economical operation of nuclear power plants. In this paper, the high temperature thermodynamic data of silicates were calculated by thermodynamic analysis. These silicates were deposited by Al, Ca and Mg with Si. The high temperature E-pH diagrams of Si-H₂O, Al-H₂O, Ca-Si-H₂O, Mg-Si-H₂O, Al-Mg-Si-H₂O and Ca-Mg-Si-H₂O were obtained at 553.15 K, 583.15 K and 613.15 K. The stable regions of solid phases and the tendencies of precipitations formation and dissolution in high temperature aqueous solution were determined. After systematic calculation and analysis, it is concluded that the dissolved substances H₃SiO₄^- and Al(OH)4^- existed stably in Si-H₂O and Al-H₂O systems under normal operation condition of PWR primary circuit, and the other systems were solid substances. With the increase of temperature, the solid phase area of each system in the primary circuit increased. The precipitations had a greater tendency to generate reaction, and were more likely to deposit on the fuel rods.