Steady state and transient multi-system coupled natural circulation tests were performed at FITY,which was scaled from typical PWR based on scaling criteria. RELAP 5 code was used to simulate the tests. The experimental and numerical analysis show that the flow rate of natural circulation was nearly unaffected by system pressure,but it increased with the increase of heating power. Steady state natural circulation was finally established after the heating power transient process and system pressure decreasing process. It was mainly influenced by the final state of transient tests.%以典型压水堆为原型堆,基于比例模化方法设计建造了自然循环试验装置(FITY),在自然循环试验装置上开展了多回路系统自然循环耦合的稳态及瞬态试验,并利用RELAP 5程序对试验工况进行计算分析.试验及计算结果表明:系统压力对自然循环流量基本无影响,自然循环流量随加热功率的增加而增加.不同降压及功率瞬变过程后均建立了稳定的自然循环,其最终状态与中间经历的瞬态过程无关.
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