[en] A test fuel assembly for the high power irradiation test was developed along the localization plan of HANARO fuel in KAERI. The test fuel assembly was manufactured based on the technical specification of HANARO fuel and the design drawings. In order to fulfill the requirement to prove HANARO fuel integrity when irradiated at a power greater than 112.8 kW/m, which was imposed during HANARO licensing, and to verify the irradiation performance of HANARO fuel, the in-pile irradiation test of HANARO fuel has been performed. Test fuel assembly was made of 30 aluminum dummy elements and 6 fuel elements which are located in the outer ring of the hexagonal fuel assembly and composed of 3 pulverized and 3 atomized U₃Si fuels. The test assembly was irradiated in CT hole for 173.7 reactor operation days with the highest neutron flux in HANARO core. The reactor physics calculations by HANAFMS showed average discharge burnup of 63 at%U-235, maximum local burnup of 77 at%U-235, average linear power of 83 kW/m and maximum linear power of 121.6 kW/m. Detailed non-destructive and destructive PIE(Post-Irradiation Examination), such as the measurement of burnup distribution, fuel swelling, clad corrosion, dimensional changes, fuel rod bending strength, micro-structure, etc. have been performed in the IMEF(Irradiated Material Examination Facility). The measured results have been analysed/compared with the predicted performance values and the design criteria described in the safety analysis report for the irradiation performance of HANARO fuel. It has been verified that HANARO fuel maintains proper in-pile performance and integrity even at the high power of 121 kW/m up to the high burnup of 77 at%U-235