Abstract A whole-core, steady-state, thermal-hydraulic model for the cylindrical pin-type fluoride-salt-cooled small modular advanced high-temperature reactor (SmAHTR) is developed. In this preconceptual reactor design initially proposed by Oak Ridge National Laboratory, each fuel assembly in the graphite-moderated core has the FLiBe coolant flowing parallel to a hexagonal array of fuel and moderator pins. The present study considers a slightly modified fuel assembly design with a hexagonal inner housing compared to the original cylindrical housing. Burnable poison pins and control rods are also included in the fuel assembly considered here. The thermal-hydraulic model employs finite volumes to solve three-dimensional conduction in the pins and the hexagonal graphite reflector regions in the core. Heat transfer between the fuel assemblies is also addressed. The finite volumes in the fluid region are modeled using a subchannel approach in which the fluid is discretized into edge, corner, and interior subchannels and the resulting mass, momentum, and energy equations are systematically solved. The subchannel model also includes the transport between adjacent subchannels both due to radial pressure gradient–driven cross flow and turbulent mixing. Appropriate closure models from the literature are used to quantify axial and lateral flow resistances, heat transfer from solid to fluid, and turbulent mixing. The resulting thermal-hydraulic model provides detailed temperature and flow information for the entire core at a modest computational cost. Preliminary verification studies are also performed and reported. Whole-core, steady-state results are presented for this SmAHTR core configuration for different power profiles. The effect of grid refinement and total mass flow rate into the core on the peak fuel temperature is also investigated. Fuel temperatures from a preliminary analysis with pin power distributions from a neutronic model are also included. The peak fuel temperature of ~1229°C in this illustrative case is below the steady-state operation limit for the SmAHTR.

中文翻译：

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氟化盐冷却小型模块化高温反应堆的稳态热工水力模型

摘要 建立了圆柱销式氟化盐冷却小型模块化先进高温堆（SmAHTR）的全堆芯稳态热工水力模型。在这种由橡树岭国家实验室最初提出的预概念反应堆设计中，石墨慢化堆芯中的每个燃料组件都有 FLiBe 冷却剂平行于燃料和慢化剂棒的六边形阵列流动。本研究考虑了与原始圆柱形外壳相比具有六边形内外壳的稍微修改的燃料组件设计。可燃毒针和控制棒也包括在此处考虑的燃料组件中。热工水力模型采用有限体积来解决针脚中的三维传导和核心中的六边形石墨反射器区域。还解决了燃料组件之间的热传递。流体区域中的有限体积使用子通道方法建模，其中将流体离散为边缘、拐角和内部子通道，并系统地求解所得质量、动量和能量方程。由于径向压力梯度驱动的横流和湍流混合，子通道模型还包括相邻子通道之间的传输。文献中的适当闭合模型用于量化轴向和侧向流动阻力、从固体到流体的热传递以及湍流混合。由此产生的热工水力模型以适度的计算成本提供了整个核心的详细温度和流量信息。还进行并报告了初步验证研究。全核，针对不同功率分布的此 SmAHTR 内核配置呈现了稳态结果。还研究了网格细化和进入堆芯的总质量流量对燃料峰值温度的影响。还包括来自中子模型引脚功率分布的初步分析的燃料温度。在此说明性案例中，~1229°C 的峰值燃料温度低于 SmAHTR 的稳态运行极限。