Abstract The unique feature of molten salt reactor (MSR) is that heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture which acts as both fuel and coolant. The fission energy from fissile fuel is released immediately into the fuel salt in the core, and the delayed neutron precursors (DNP) have a loss due to fuel circulation in the primary loop, which both make MSR be characterized by the strong interplay between the neutronics and thermal hydraulics (TH) and imply that the software developed for traditional solid-fueled reactors is not applicable to MSR. In this study, a new coupled neutronics and TH code named TMSR3D is developed for evaluating the steady-state characteristics of liquid-fueled MSR. In this code, the fourth order standard nodal expansion method (NEM) is implemented to solve the neutron diffusion equations, and the parallel multi-channel model is adopted to take into account the feedbacks of local temperature to group constants. Besides, a convection term is introduced into the traditional balance equations for DNP to consider the influence of fuel salt flow. Some experiment data of Molten Salt Reactor Experiment (MSRE) are chosen to verify the code, and the core characteristics including the distributions of neutron fluxes, DNP and temperature under the rated condition are simulated and discussed. Furthermore, the impacts of the inlet mass flow rate, inlet fuel temperature and the fuel salt residence time out of the core are analyzed in detail. The numerical results indicate that the TMSR3D code can provide a reliable description of the neutronics-TH coupling phenomena and of the steady state analysis for graphite-moderated channel-type MSRs.

中文翻译：

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基于节点膨胀法的熔盐堆稳态分析程序开发

摘要 熔盐反应堆（MSR）的独特之处在于重金属燃料和裂变产物可以溶解在熔融氟化物盐中，形成一种兼具燃料和冷却剂作用的共晶混合物。裂变燃料的裂变能立即释放到堆芯的燃料盐中，延迟中子前体（DNP）由于燃料在初级回路中循环而损失，这都使 MSR 具有中子之间强相互作用的特点。和热工水力 (TH) 并暗示为传统固体燃料反应堆开发的软件不适用于 MSR。在这项研究中，开发了一种名为 TMSR3D 的新耦合中子学和 TH 代码，用于评估液体燃料 MSR 的稳态特性。在这段代码中，采用四阶标准节点展开法(NEM)求解中子扩散方程，采用并行多通道模型考虑局部温度对群常数的反馈。此外，在传统的DNP平衡方程中引入了对流项，以考虑燃料盐流的影响。选取熔盐反应堆实验(MSRE)的部分实验数据对程序进行验证，对额定工况下的中子通量分布、DNP、温度等堆芯特性进行了模拟和讨论。此外，详细分析了入口质量流量、入口燃料温度和燃料盐在堆芯外的停留时间的影响。