Critical heat flux (CHF) tests using SMART fuel bundles have been conducted to provide database for the development of a CHF correlation which is essential for the evaluation of the thermal design criteria and safety analysis of SMART. A series of experiments was carried out to investigate the thermal mixing and CHF in 5 X 5 test bundles with uniform and non-uniform axial power shapes. A high-pressure water test loop included pressure housing with 5 X 5 SMART fuel simulators, high-head pump, pressurizer with non-condensable gas, heat exchangers, preheater and mixers. The CHF experiments varied the pressure from 2.5 to 17 MPa and the mass flux from 200 to 2500 kg/m2 s which covers the normal operating conditions as well as the AOO (anticipated operational occurrences) for SMART. Several hundreds of CHF data items obtained from the water loop CHF experiments were employed for the development and validation of a CHF correlation which was applied to the thermal design and safety analysis of SMART.