A radioactivity analysis of OREOX and the sintering steps for the DUPIC fuel fabrication process has been conducted. This study utilized ORIGEN2 code to calculate and analyze the radioactivity of spent fuels for various burn-up and cooling times. The analysis results have shown that the activity reduction of spent fuels after DUPIC fuel fabrication process was 40∼51 % and higher with longer burn-up and cooling times. This study also shows that the distribution of gaseous waste generated from OREOX process is mainly attributed to Kr, Ru and H-3, regardless of burn-up and cooling times. On the other hand, in the off-gas of the sintering process, the radioactivity distribution of Cs is more than 98 %, regardless of burn-up and cooling times.