Molten salt reactors (MSRs) have gained worldwide interest in recent years due to their appealing safety and resource utilisation characteristics. These reactors have a unique feature, i.e. the presence of nuclear fuel in the form of a molten fluoride or chloride salt containing the fissile and fertile materials. The fuel salt also acts as the coolant, and this dual role results in a complex, highly coupled multiphysics system which poses a challenge in modelling and simulation of MSRs. This paper presents the development of a simulation model for the Molten Salt Fast Reactor (MSFR) to predict the behaviour of inert gas bubbles in the core and to quantify their impact on the reactivity. Inert gas bubbles in MSFR have been modelled using a multiphysics approach coupling computational fluid dynamics for fluid flow and heat transfer with neutron diffusion equation for neutronics and a balance equation with diffusion and advection terms for taking into account the drift of the delayed neutron precursors. The two-phase flow has been modelled using a simplified Euler–Euler model for small volume fraction of the dispersed phase, i.e. for small bubble fraction, which combines the momentum and continuity equation of the liquid and gas phases and adds a gas-phase transport equation to track the void fraction. Simulations reveal that the bubble distribution in the core has a significant impact on reactivity resulting in a difference in the bubbling feedback coefficient compared to studies using a homogeneous distribution.

熔融盐反应堆（MSR）近年来因其吸引人的安全性和资源利用特性而引起了全世界的关注。这些反应堆具有一个独特的特征，即以易裂变和肥沃材料形式存在的熔融氟化物或氯化物盐形式的核燃料的存在。燃油盐还充当冷却剂，这种双重作用导致了一个复杂的，高度耦合的多物理场系统，这对MSR的建模和仿真提出了挑战。本文介绍了熔融盐快堆（MSFR）的仿真模型的开发，以预测堆芯中惰性气泡的行为并量化其对反应性的影响。MSFR中的惰性气泡已采用多物理场方法进行建模，该方法将流体流动和传热的计算流体动力学与中子学的中子扩散方程以及具有扩散和对流项的平衡方程相结合，以考虑到延迟中子前体的漂移。已使用简化的Euler–Euler模型对两相流进行了建模，该模型针对的是分散相的小体积分数，即小气泡分数，该模型结合了液相和气相的动量和连续性方程，并增加了气相传输方程来跟踪空隙率。模拟显示，与使用均质分布的研究相比，岩心中的气泡分布对反应性具有重大影响，从而导致冒泡反馈系数有所不同。已使用简化的Euler–Euler模型对两相流进行了建模，该模型针对的是分散相的小体积分数，即小气泡分数，该模型结合了液相和气相的动量和连续性方程，并增加了气相传输方程来跟踪空隙率。模拟显示，与使用均质分布的研究相比，岩心中的气泡分布对反应性具有重大影响，从而导致冒泡反馈系数有所不同。使用简化的Euler–Euler模型对两相流进行了建模，该模型用于较小的分散相体积分数，即用于较小的气泡分数，该模型结合了液相和气相的动量和连续性方程，并增加了气相传输方程来跟踪空隙率。模拟显示，与使用均质分布的研究相比，岩心中的气泡分布对反应性具有重大影响，从而导致冒泡反馈系数有所不同。