Analysis of Reasons for Abnormal Enrichment of Silica in Pressurized Water Reactor

The SiO₂ leaching behavior and mechanism of glass filter element were studied using static immersion method. The effects of temperature, pH value of the coolant and filter accuracy on the evolution of SiO₂ were investigated. The results show that the rate of SiO₂ evolution rapidly decreases and tends towards stability over 60 day attributed to the formed colloid stable film on the surface of filter. The rate of SiO₂ evolution obviously increases with the temperature. It’s 0.009 8 g/(m²•d) at 298 K, and about an order of magnitude lower than that at 343 K (0.204 g/(m²•d)), demonstrating the process of SiO₂ evolution is not simple ion diffusion or dissolution reaction, but controlled by both reactions, even more complex. At the same condition, the higher the filter accuracy is, the faster the rate of SiO₂ evolution is.