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Experiment to investigate the mechanism of boiling heat transfer in a narrow gap on severe accident scenarios of TMI-2 nuclear power plant is necessary to develop the understanding of the related accident management.The present study aimed to obtain heat flux value and critical heat flux (CHF) during boiling heat transfer process in a narrow gap of annulus. The study was experimentally carried out using the HeaTiNG 01 test with water as cooling fluid which temperature was varied at 75°C, 85°C dan 95°C. The rod was heated to 650°C. The boiling process during cooling was investigated by recording the transient temperature of the heated rod. The data was used to calculate the heat flux and wall superheat which results were represented in a boiling curve. The experimental results showed that the CHF value of the cooling media at 75°C was lower compared with that of at 85°C and 95°C. It was found that the values of CHF at 85°C and 95°C were close. The maximum CHF value at 75°C was 230 kW/m2 , while at 95°C was 282 kW/m2 . The CHF values at various position of heated rod was found to follow polynomial correlation. By comparing the boiling film areas from experimental results with that of Bromley correlation, it was concluded that boiling process in a narrow gap could not categorized as pool boiling process