本文以小型一体化自然循环反应堆为研究对象,用REL A P5/M OD3.2对反应堆系统、中间回路及二回路系统进行建模,对反应堆单双环路切换及偏环路运行时反应堆的自然循环运行特性进行数值模拟研究.计算结果表明:在反应堆自然循环运行工况下,进行单双环路切换及偏环路运行时,堆芯能重新建立稳定的自然循环.双环路切换至单环路后,堆芯出口温度降低,堆芯自然循环平衡流量降低但仍大于初始值的1/2;单环路切换至双环路运行时,堆芯流量、温度均与双环路稳定工况的一致;偏环路运行时故障环路循环流量降低,正常环路自然循环流量升高,堆芯总流量降低的数值为二者之差.%The small nuclear power plant was aimed as a reference in this work ,and the models of the reactor coolant system ,the intermediate and the secondary loop system were established by RELAP5/MOD3.2 . The transition processes of single to double loop switch of the reactor and asymmetric loop operation were simulated to analyze the natural circulation characteristics .The results show that when the reactor switches from single to double loop operation and asymmetric loop operation under natural circulation , the core can rebuild stable natural circulation operation .In the case of double to single loop operation ,core outlet temperature and flow rate reduce ,but the flow rate is grea-ter than 1/2 of the original flow rate .In the case of single to double loop operation ,core outlet temperature and flow rate are consistent with those of steady state .In the case of asymmetric loop operation ,the flow rates of core and fault loop reduce ,but the flow rate of normal loop increases and the decrease in total flow rate is the difference between the flow rates of two loops .
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