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Multiphysics Running-In Simulations for Pebble-Bed Reactors with Griffin.

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Bibliographic Details
Title: Multiphysics Running-In Simulations for Pebble-Bed Reactors with Griffin.
Authors: Hanophy, Joshua1 (AUTHOR) joshua.hanophy@inl.gov, Balestra, Paolo1 (AUTHOR), Wang, Yaqi1 (AUTHOR), Ortensi, Javier1 (AUTHOR), Schunert, Sebastian1 (AUTHOR)
Source: Nuclear Science & Engineering. 2026 Suppl 1, Vol. 200, pS644-S658. 15p.
Subject Terms: *Pebble bed reactors, *Computer simulation, *Transient analysis, *Fluid flow, *Heat transfer
Abstract: Griffin, a Multiphysics Object-Oriented Simulation Environment (MOOSE)–based application targeting transient modeling of advanced reactors, has been used recently to model pebble-bed reactors (PBRs). The modeling effort has focused thus far on equilibrium core calculations. A new capability to simulate the running-in phase of PBR operation has been added to Griffin. This work demonstrates the new capability with a coupled multiphysics running-in simulation. Griffin computes power densities in the core at each time step of the running-in simulation and passes these to Pronghorn, which models fluid flow and heat transfer to calculate pebble surface temperatures. These surface temperatures are used along with the power densities in a heat conduction model to compute average fuel and moderator temperatures, which are passed back to Griffin and accounted for with temperature-dependent cross sections. This work also describes a novel methodology for determining appropriate pebble feed rates and control rod positioning during the running-in simulation. The RZ-geometry model used in this work requires minimal computational resources and can be used for optimization and uncertainty studies in future works. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:Griffin, a Multiphysics Object-Oriented Simulation Environment (MOOSE)–based application targeting transient modeling of advanced reactors, has been used recently to model pebble-bed reactors (PBRs). The modeling effort has focused thus far on equilibrium core calculations. A new capability to simulate the running-in phase of PBR operation has been added to Griffin. This work demonstrates the new capability with a coupled multiphysics running-in simulation. Griffin computes power densities in the core at each time step of the running-in simulation and passes these to Pronghorn, which models fluid flow and heat transfer to calculate pebble surface temperatures. These surface temperatures are used along with the power densities in a heat conduction model to compute average fuel and moderator temperatures, which are passed back to Griffin and accounted for with temperature-dependent cross sections. This work also describes a novel methodology for determining appropriate pebble feed rates and control rod positioning during the running-in simulation. The RZ-geometry model used in this work requires minimal computational resources and can be used for optimization and uncertainty studies in future works. [ABSTRACT FROM AUTHOR]
ISSN:00295639
DOI:10.1080/00295639.2025.2497025