Evaluating turbulence modeling for thermal–hydraulics analysis of molten salt reactors

Abstract

This article studies the impact of Reynolds Averaged Navier Stokes (RANS) turbulence modeling for the thermal–hydraulics analysis of open-core molten salt reactors (MSRs). The first part of the article describes the $k-ϵ$ and $k-\omega$ SST RANS turbulence models recently introduced to Pronghorn in the Idaho National Laboratory’s (INL) Multiphysics Object-Oriented Simulation Environment (MOOSE). Special attention is given to the near-wall flow modeling strategies implemented in both models and their computational implementation in MOOSE. Both models are validated for canonical experimental data that resemble the flow phenomena expected for MSRs: a channel flow, a backward facing step, and swirling flow in a curved pipe. These models are then applied to the open-source specifications of the Molten Chloride Reactor Experiment (MCRE), which is named Lotus Molten Salt Reactor (L-MSR) for conciseness. First, the flow phenomena and pressure drops predicted by both models are compared with higher-fidelity LES simulations for the expected reactor operational conditions. Then, the impact of the selected turbulence model on steady-state temperature fields distribution is evaluated. Finally, recommendations are given for the selected approach to turbulence modeling of open-core MSRs.