压水堆核电站硅含量异常升高原因分析

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

采用静态浸泡法研究了玻璃纤维滤芯在硼锂水溶液中SiO2的浸出行为及浸出机理,探讨了温度、pH值、过滤精度对SiO2浸出行为的影响。实验结果表明:SiO2浸出率随浸泡时间的延长而迅速减小,60d后逐渐趋于稳定值,表明滤芯表面生成一层胶体保护膜。浸出速率随温度的升高显著增大,过滤精度为0.6μm的滤芯在浸泡最初的4d,298K时的浸出速率(0.009 8g/(m2·d))较343K时的浸出速率(0.204g/(m2·d))约低1个数量级,说明SiO2浸出过程不是单一的离子扩散反应或网络溶解反应,而是两者共同参与或多种机制共同控制的复杂过程;相同条件下,玻璃纤维的过滤精度越高,浸出SiO2的速率越大。

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 8g/(m2·d)at 298 K,and about an order of magnitude lower than that at 343K(0.204g/(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.