NEAMS IRP Challenge Problem 3: Mixing in Large Enclosures and Thermal Stratification

A. Manera, A. S. Iskhakov, V. C. Leite, Jiaxin Mao, C. Tai, V. Vishwakarma, R. Wiser, E. Baglietto, I. A. Bolotnov, N. T. Dinh, Y. Hassan, V. Petrov, E. Merzari

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

Mixing in large enclosures and thermal stratification play an important role in several advanced reactor designs, including liquid metal cooled reactors and high temperature gas reactors. Lessons learned from a recent international benchmark [1] using system-level codes for the simulations of Sodium-Cooled Fast Reactors (SFRs) have pointed out that, in order to improve the predictive capabilities of system codes, model developments are needed to correctly capture mixing and thermal stratification in the reactor hot pool upper plenum, the propagation of stratification fronts, and the overall effect of thermal stratification and mixing on natural circulation and heat transfer between primary and intermediate loops. CFD codes have also been shown to under-perform when simulating buoyancy-driven flows, yielding inaccurate predictions of the extension and propagation of stratified fronts. This is because the simulation and transport of scalar quantities (e.g., temperature, density, species concentration, etc.) in current CFD RANS-based turbulence models rely on the Simple Gradient-Diffusion Hypothesis (SGDH) to take into account turbulent fluxes whereas a simplified model to take into account turbulent kinetic energy production and dissipation induced by density differences. The NEAMS IRP Challenge Problem 3 (CP3) seeks to develop a multi-fidelity, multi-scale set of models for the mixing in large enclosures with or without thermal stratification, from CFD URANS to system-level code models including reduced order models (ROMs) in order to provide accurate and computationally affordable predictions for mixing and stratification in large enclosures. This Challenge Problem generalizes specific needs related to the TerraPower, Westinghouse and General Atomics designs by developing a set of benchmarks in order to advance, demonstrate and quantify the accuracy of mixing and stratification in large plena. Results of high-resolution experiments and LES/DNS are used in combination with machine learning techniques to feed the development of lower fidelity models, following a hierarchical approach. In the paper an overview of the ongoing experimental and modeling activities is presented.

Original languageEnglish (US)
Title of host publicationProceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
PublisherAmerican Nuclear Society
Pages4476-4488
Number of pages13
ISBN (Electronic)9780894487934
DOIs
StatePublished - 2023
Event20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023 - Washington, United States
Duration: Aug 20 2023Aug 25 2023

Publication series

NameProceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023

Conference

Conference20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
Country/TerritoryUnited States
CityWashington
Period8/20/238/25/23

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Instrumentation

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