The complex core geometry of Pebble Bed Reactors (PBRs) necessitates multiscale techniques for fast-turnaround design and analysis. This paper describes the multiscale model implemented in the Pronghorn PBR simulation tool and demonstrates application to steady-state analysis of the Mark-1 Pebble Bed Fluoride-Salt-Cooled High-Temperature Reactor (PB-FHR). Verification of the pebble model with fully-resolved heat conduction shows that material-wise pebble temperatures are predicted to within 10°C over a wide range in thermal conditions. Anisotropic drag models are correlated for the outer reflector blocks using COMSOL, providing closures for modeling of bypass flows. With a porous media model of the outer reflectors, the core bypass fraction and fuel, reflector, and structural material temperatures are predicted for a number of different inflow conditions. This work demonstrates the full-core analysis capabilities of the Pronghorn application and enables comprehensive reactor analysis with the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework.

卵石床反应器（PBR）的复杂堆芯几何形状需要采用多尺度技术来进行快速周转设计和分析。本文介绍了在Pronghorn PBR仿真工具中实现的多尺度模型，并演示了其在Mark-1卵石床氟化物-盐-盐冷却的高温反应器（PB-FHR）的稳态分析中的应用。对具有完全解析的热传导的卵石模型的验证表明，在热条件下，按材料分类的卵石温度在很宽的范围内预计将在10°C以内。各向异性阻力模型使用COMSOL与外部反射器模块相关联，从而为旁路流的建模提供了闭包。利用外部反射器，堆芯旁通分数和燃料反射器的多孔介质模型，可以预测许多不同流入条件下的结构温度和材料温度。这项工作演示了Pronghorn应用程序的全核分析功能，并通过Multiphysics面向对象的仿真环境（MOOSE）框架实现了全面的反应堆分析。