The application of lead–bismuth small modular reactor (SMR) has unique advantages in offshore engineering. Moving conditions caused by ocean environment are important for the security analysis of nuclear system. In this paper, the models including core neutronics, reactor thermal hydraulics and moving conditions for a natural circulation lead–bismuth reactor with thermal power of 5 MW are established. The calculation results show that (a) inclination causes core flowrate reduction and coolant temperature rise at the core outlet, maximum of which can be 20% and 20 ℃. (b) Heaving and rolling conditions both result in fluctuation of core mass flow rate and fuel cladding temperature while pattern of each differs. Flowrate fluctuation larger than 10% of the steady state happens under large heaving condition. Backflow appears in the heat exchanger if the rolling condition is strong enough. (c) Lead–bismuth SMR is influenced more intensely under heaving and rolling condition compared with small PWR. 18% larger mass flowrate fluctuation appears in the lead–bismuth SMR under heaving acceleration of 0.5 g. Opposite trend of time-domain average core flowrate appears for two reactors under rolling condition. This study provides theoretical basis for the thermal–hydraulic system analysis of lead–bismuth SMR under moving conditions.

铅铋小型模块化反应堆（SMR）的应用在海上工程中具有独特的优势。海洋环境引起的运动条件对核系统的安全分析很重要。在本文中，建立了包括核心中子学，反应堆热工水力和热功率为5 MW的自然循环铅铋反应堆的运动条件的模型。计算结果表明：（a）倾斜会导致堆芯流量减少，堆芯出口处的冷却液温度升高，最高可达20％和20℃。（b）起伏和滚动条件均导致芯质量流量和燃料包壳温度的波动，而两者的模式不同。在大的起伏情况下，流量波动大于稳态的10％。如果滚动条件足够强，则热交换器中会出现回流。（c）与小压水堆相比，铅铋SMR在起伏和滚动条件下受到的影响更大。在0.5 g的加速度下，铅铋SMR的质量流量波动增加了18％。在滚动条件下，两个反应堆出现了时域平均堆芯流量的相反趋势。该研究为运动条件下铅铋SMR的热工液压系统分析提供了理论依据。在滚动条件下，两个反应堆出现了时域平均堆芯流量的相反趋势。该研究为运动条件下铅铋SMR的热工液压系统分析提供了理论依据。在滚动条件下，两个反应堆出现了时域平均堆芯流量的相反趋势。该研究为运动条件下铅铋SMR的热工液压系统分析提供了理论依据。