The study of core conversion of the IRT research reactor from the HEU to LEU fuels has been conducted in this paper. Fuel burnup, buildup of actinides and fission product inventory for the IRT research reactor with UO2-Al dispersion fuel for the various different uranium enrichments and the uranium density such as: (IRT-3M 90% 1.1 g/cm3, IRT-3M 36% 2.51 g/cm3, IRT-4M 19.75% 3.25 g/cm3, IRT-4M 19.75% 3.48 g/cm3, IRT-4M 19.75% 3.71 g/cm3) have been carried out using the GETERA code. The multiplication factor (keff) of the IRT-3M and IRT-4M reactors were calculated using the MCNP4C code. The results showed, after 200 days of the reactor operation time that the total consumptions of 235U for the five cases were 73.85, 73.13, 72.66, 72.80 and 73.21 g respectively. The amounts of 239Pu produced in the core were: 0.43, 3.39, 5.90, 6.13 and 6.35 g respectively. The total radioactivities of fuel assembly were: 2.78E+15, 2.83E+15, 2.86E+15, 2.88E+15 and 2.89E+15 Bq respectively. Finally, from the neutronic view point, the LEU fuel was validated to be a suitable candidate for the fuel conversion of the IRT in the future. Keywords: Burnup, IRT reactor, HEU, LEU, GETERA code, Fission products