自然循环对压力容器液位测量的影响

The impact on vessel level measurement due to natural circulation

对CPR1000核电站一回路自然循环对堆芯冷却监测系统CCMS(Core Cooling and Monitoring System)压力容器液位L VSL测量引入的误差进行了量化计算,结合状态导向法事故运行程序SOP(State Oriented Procedure),分析了自然循环所引起的压力容器液位测量误差对SOP的影响。分析结果表明,由于SOP采用多重参数对机组状态进行诊断,该误差不会阻碍事故处理关键安全操作的执行。

Background： The Core Cooling and Monitoring System （CCMS） of CPR1000 nuclear power station supplies monitoring means for two primary state functions defined in State Oriented Procedure （SOP）. Purpose： We aim to deal with the errors caused by L VSL measurement and discuss the influence on SOP accident treatment. Methods： The calculation formula of natural recirculation flow rate was estimated. The maximum flow rates of single phase natural recirculation （at the time of reactor trip） and two phase natural recirculation （the void fraction in hot leg was 0.2） were calculated. The impact on SOP due to the measurement error of L VSL was analyzed. Results： Firstly, in the condition of single phase recirculation, the estimated error of L VSL measurement induced by the natural recirculation was less than 1.6%. Secondly, in the condition of two phase natural recirculation, the natural recirculation induced an over-estimated error about 3.6% to L VSL measurement when the void fraction in hot leg was 0.2. Conclusion： As multi-parameters are adopted for SOP to diagnose the core cooling state, the implementation of the safety related operations is guaranteed.