压水堆核电厂安注管线内不凝结性气体聚集现象仿真研究

Sation Study on Noncondensable Gas Accumulation Phenomenon in Safety Injection Piping System of PWR NPP

核电厂发生失水事故和蒸汽管道断裂事故时,安全注入系统用来执行堆芯应急冷却功能。在正常运行工况下,系统将长时间处于备用状态,导致安注管线内易出现不凝结性气体聚集产生死管段,因此,需定期检查安注管线是否处于满水状态。本文基于流体仿真软件COMSOL建立管道模型,综合考虑温度波动对空气在水中溶解度的影响,对充水管道内不凝结性气体聚集现象进行仿真研究。结果表明,外界温度在一天之内呈现正弦规律小幅度波动时,管道内的空气随温度升高而析出,随温度降低而溶解。约25d后,管道内每天的最大和最小空气体积分数趋于稳定,因此,安注系统管线的排气操作应以不低于每25d一次的频度执行。

The safety injection system,which provides emergency core cooling under LOCA accident and steam tube rupture accident.Under normal operating conditions,the system will be in standby state for a long time.Therefore,dead-end pipe phenomenon may occur in safety injection piping system as a result of non-condensable gas accumulation.Thus,surveillance is needed to verify if the piping system is full of water.Based on computational fluid dynamics software COMSOL,a numerical mode with the consideration of effect of temperature on the solubility of air in the water was built to investigate non-condensable gas accumulation phenomenon in a pipe full of water.The numerical results showed that,when the environment temperature waes in the sine function with small amplitude every daytime,the air in the pipe will dissolved as the temperature increases,on the contrary,the air in the pipe will precipitate out as temperature decreases.After about 25 d,the maximum and minimum air volume fraction in the pipe during one day are both stabilizing,therefore,the exhaust operation of safety injection system piping should be performed in a frequency longer than once in 25 d.