<p>Nuclear research reactors serve as a source of neutrons, unlike power reactors, which are mainly used for electricity generation. The research reactors serve diverse objectives, including fundamental physics research, isotope production, neutron activation analysis for forensic and other studies, etc. Testing of structural materials and new fuels is also carried out in research reactors, in addition to training of manpower for the nuclear field. Thermal hydraulics in research reactors with lower power densities were often characterized by high thermal margins. However, for the high-flux research reactors, maintaining a high degree of safety margins is not practically feasible. Thus, a comprehensive approach is needed for the thermal-hydraulic design and qualification of such high-flux research reactors. The application of best-estimate codes for thermal-hydraulic analyses, complemented by advanced computational fluid dynamics (CFD) studies, appears to be the most prudent approach. Furthermore, realistic thermal margins could be determined for different postulated initiating events (PIEs) and accident scenarios by statistical treatment of design and fabrication uncertainties, also known as best estimate plus uncertainty (BEPU) methodology, to achieve a high degree of confidence in the code predictions. Experimental studies are also required for a better understanding of the heat transfer phenomenon used for the estimation of thermal margins against the onset of nucleate boiling (ONB) and departure from nucleate boiling (DNB) specific to fuel geometries employed in the reactor. This work provides a comprehensive overview of the thermal-hydraulic considerations for nuclear research reactors and outlines the strategies implemented for safety analyses to assess thermal margins during design qualification.</p>