Multiscale thermal-hydraulic modeling of the pebble bed fluoride-salt-cooled high-temperature reactor

A. J. Novak, S. Schunert, R. W. Carlsen, P. Balestra, R. N. Slaybaugh, R. C. Martineau

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Article number107968
JournalAnnals of Nuclear Energy
StatePublished - May 2021
Externally publishedYes


  • PB-FHR
  • PBR
  • Porous media
  • Pronghorn

ASJC Scopus subject areas

  • Nuclear Energy and Engineering


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