The fluoride-salt-cooled high-temperature reactor (FHR) is a Generation IV nuclear energy system with huge potential for further development. Owing to its unique advantages, such as inherent safety, high economical potential, small modular design, environmental adaptability, and nonproliferation, FHRs have been the focus of considerable attention. In this study, the history and characteristics of FHR are reviewed first, including the concept initiation and active exploration stages. Then, the research status of FHR is introduced, which is about the state of the art in primary coolant systems, structural materials, key equipment, energy conversion systems, direct reactor auxiliary cooling systems, nuclear fuel, tritium control strategies, and experimental studies. Furthermore, the challenges faced by FHR technology are summarized, including corrosion of structural materials, optimization of energy conversion systems, solidification of fluoride salts, control of tritium, control of beryllium contamination, enrichment of lithium fluoride-beryllium fluoride salt, design of core refueling, and operation and control of pebble bed reactor. Based on the above, the focuses of research on FHR design are discussed, and areas of study for future development of FHR technology are recommended. This paper aims to provide a reference for the research and development of FHR in the future. 

Fluoride-salt-cooled high-temperature reactors: Review of historical milestones, research status, challenges, and outlook

Large eddy simulations of the all-speed turbulent jet flow using 3-D CFD code GASFLOW-MPI

Large eddy simulations of erosion of a stratified layer by a buoyant jet

Synthesis of a CFD benchmark exercise based on a test in the PANDA facility addressing the stratification erosion by a vertical jet in presence of a flow obstruction

Many countries consider hydrogen as a promising energy source to resolve the energy challenges over the global climate change. However, the potential of hydrogen explosions remains a technical issue to embrace hydrogen as an alternate solution since the Hindenburg disaster occurred in 1937. To ascertain safe hydrogen energy systems including production, storage, and transportation, securing the knowledge concerning hydrogen flammability is essential. In this paper, we addressed a comprehensive review of the studies related to predicting hydrogen flammability by dividing them into three types: experimental, numerical, and analytical. While the earlier experimental studies had focused only on measuring limit concentration, recent studies clarified the extinction mechanism of a hydrogen flame. In numerical studies, the continued advances in computer performance enabled even multi-dimensional stretched flame analysis following one-dimensional planar flame analysis. The different extinction mechanisms depending on the Lewis number of each fuel type could be observed by these advanced simulations. Finally, historical attempts to predict the limit concentration by analytical modeling of flammability characteristics were discussed. Developing an accurate model to predict the flammability limit of various hydrogen mixtures is our remaining issue.

Recent Progress in Hydrogen Flammability Prediction for the Safe Energy Systems

Kairos power thermal hydraulics research and development

Neutronics, thermal-hydraulics, and multi-physics benchmark models for a generic pebble-bed fluoride-salt-cooled high temperature reactor (FHR)

One of the most important parameters in the analysis of containment safety of the light water reactors during a loss of coolant accident (LOCA) is the prediction of the hydrogen concentration. To ensure proper design of the containment and to mitigate the fire/explosive risk created by the flammable hydrogen gas, this concentration build up must be analyzed. Lumped parameter (LP) codes are the main tools used in containment thermal-hydraulic analysis; however, they are limited when it comes to scenarios which require higher fidelity analysis of local phenomena. While the use of computational fluid dynamics (CFD) allows for higher fidelity analyses, CFD requires a comprehensive validation study due to turbulence and condensation modeling. During a LOCA accident, the leaked hydrogen from the primary circuit can form a stable stratified layer at the top of the containment building. The formation and erosion of a stratified layer is a challenging numerical problem due to the interaction mechanism of the jet flow with the stratified layer. The OECDNEA conducted an experiment at the Paul Scherrer Institute (PSI) as part of the third International Benchmark Study (IBE-3) to investigate the erosion of the stratified layer by a vertical air-helium jet from the bottom of the large vessel (height 8 m. diameter 4 m.). During the experiment, CFD grade experimental data was generated that could be used for comparative studies. In the present study, the experiment is simulated by using the STAR-CCM+ CFD code with various turbulence models including Reynolds-Averaged Navier-Stokes (RANS) models and Large Eddy Simulation (LES). The Realizable k-ε and k-ω SST showed good agreement with the experimental data when predicting the erosion of the stratified layer and global mixing of the gas components; specifically an anisotropic analysis with RSM showed similar behavior with the isotropic two equations model for the erosion of the stratified layer. The LES model also showed faster erosion than experimental data, while the cost of the LES simulation was much higher than RANS simulations. The current validation study contributes to the sensitivity analysis of the turbulence models for erosion behavior in the stratified layer. In addition to that, the results of this study will provide a foundation to discuss the feasibility of the CFD code usage in containment level thermal hydraulic analysis.

CFD Simulations of Erosion of a Stratified Layer by a Buoyant Jet in a Large Vessel

......................................................................................................................ii ACKNOWLEDGEMENTS .............................................................................................. iv CONTRIBUTORS AND FUNDING SOURCES .............................................................. v TABLE OF CONTENTS .................................................................................................. vi LIST OF FIGURES ........................................................................................................ viii LIST OF TABLES ......................................................................................................... xiii CHAPTER

Fatih Sinan Sarikurt

Papers

Kairos power thermal hydraulics research and development

Large eddy simulations of erosion of a stratified layer by a buoyant jet

Neutronics, thermal-hydraulics, and multi-physics benchmark models for a generic pebble-bed fluoride-salt-cooled high temperature reactor (FHR)

CFD Simulations of Erosion of a Stratified Layer by a Buoyant Jet in a Large Vessel

Multi-Scale CFD Simulations of Momentum and Buoyancy Driven Flows in Nuclear Reactor Systems