Abstract In recent years, the FNPP (Floating Nuclear Power Plant) has got more and more attention and rapid development due to very wide prospect application on remote areas or islands. In general, the IPWR (Integral Pressurized Water Reactor) is adopted to meet the requirements of the limited space, the nuclear safety and the maneuverability in marine. The IPWR could depend on natural circulation operation to remove the residual heat of core under accident conditions or low load operation condition. Because the driving head is low, the natural circulation flow in many parallel channels is likely to be influenced by ocean motion and thermonuclear coupling effect. Among various kinds of ocean motions, the rolling motion will introduce the additional force pressure drop and change the gravity pressure drop with time, so the force acting on coolant in the assemblies will be more complex. In order to clarify the natural circulation flow characteristics of the core in FNPP in rolling motion, based on the modified RELAP5 code by adding the ocean motion module and spatial coordinate convert module, the neutron physics and thermal-hydraulic coupled model of IPWR was been established. The core three-dimensional distribution, the radial cross-section and axial distribution of main thermal-hydraulic parameters were obtained. The effect of the tangential force pressure drop, the centripetal force pressure drop and the gravity pressure drop on the coolant in the core in rolling motion were discussed. The results showed that the natural circulation flow rate fluctuates periodically with the rolling motion. And the time-varying gravity pressure drop is the main effect factor of fluctuation. Because of the structure of IPWR is compact, the rolling radius is relatively short, the effect of the general rolling motion on the natural circulation flow distribution of the core is not obvious. The coolant temperature and the fuel power distribution of the core periphery fluctuates slightly, and the reactivity feedback introduced by the coolant temperature and the fuel temperature fluctuation is relatively small. In consequence, the FNPP in the movable marine platform in natural circulation mode operation is safety in general rolling motion.

中文翻译：

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浮动式核电站堆芯滚动自然循环流动特性

摘要 近年来，FNPP（浮动核电站）由于在偏远地区或岛屿上的应用前景非常广泛，受到越来越多的关注和快速发展。一般采用IPWR（Integral Pressurized Water Reactor）来满足有限空间、核安全和海上机动性的要求。IPWR 可以依靠自然循环运行来去除事故工况或低负荷运行工况下堆芯的余热。由于驱动水头低，许多平行通道的自然循环流动很可能受到海洋运动和热核耦合效应的影响。在各种海洋运动中，横摇运动会引入附加力压降并随时间改变重力压降，因此作用在组件中冷却剂上的力会更加复杂。为明确FNPP堆芯在横摇运动时的自然循环流动特性，在修改后的RELAP5代码基础上，增加海洋运动模块和空间坐标转换模块，建立IPWR的中子物理与热工水力耦合模型. 获得了岩心三维分布、主要热工水力参数的径向截面和轴向分布。讨论了切向力压降、向心力压降和重力压降对滚动运动中芯内冷却剂的影响。结果表明，自然循环流量随滚动运动呈周期性波动。而时变重力压降是波动的主要影响因素。由于IPWR结构紧凑，滚动半径较短，一般滚动运动对堆芯自然循环流分布的影响不明显。堆芯外围冷却剂温度和燃料动力分布波动较小，冷却剂温度和燃料温度波动引入的反应性反馈较小。因此，自然循环模式操作的可移动海洋平台中的FNPP在一般滚动运动中是安全的。堆芯外围冷却剂温度和燃料动力分布波动较小，冷却剂温度和燃料温度波动引入的反应性反馈较小。因此，自然循环模式操作的可移动海洋平台中的FNPP在一般滚动运动中是安全的。堆芯外围冷却剂温度和燃料动力分布波动较小，冷却剂温度和燃料温度波动引入的反应性反馈较小。因此，自然循环模式操作的可移动海洋平台中的FNPP在一般滚动运动中是安全的。