An integrated open-source CFD workflow for gas distribution and flame propagation analysis in nuclear reactor safety

A coupled numerical simulation workflow for comprehensive end-to-end analysis of nuclear reactor accidents is introduced with the emphasis on two distinct, open-source Computational Fluid Dynamics (CFD) codes developed within the OpenFOAM framework: containmentFOAM for detailed simulation of pre-ignition gas distribution and thermal-hydraulics, and explosionDynamicsFOAM for the subsequent flame propagation analysis. A Small Break Loss-of-Coolant Accident (SB–LOCA) scenario in a generic Pressurized Water Reactor (PWR) containment is analyzed, providing critical insights into containment safety, quantifying pre-ignition turbulence, pressure evolution, maximum flame speed, and resolving local flow phenomena such as inter-compartmental gas flows and multiple emerging flame paths. A key improvement of accident analysis in the present work is in the use of a full-scale CFD simulation for obtaining the spatially-resolved turbulence kinetic energy field prior to ignition. This allowed choosing the appropriate combustion modeling approach in the subsequent flame propagation simulation. For the specific SB–LOCA scenario investigated here, the simulations indicated that the flame propagation remained within the deflagration regime, i.e. the flame speeds necessary for a Deflagration-to-Detonation Transition (DDT) were not achieved within the containment volume. • End-to-end SB-LOCA analysis: gas mixing to flame propagation. • Coupled LP-CFD workflow: COCOSYS, containmentFOAM & explosionDynamicsFOAM. • Full-scale PWR containment CFD simulations. • Realistic pre-ignition turbulence fields for initializing the flame propagation CFD. • Flame remains in deflagration regime; no DDT for analyzed SB-LOCA scenario.