The 5-MW highly enriched uranium (HEU)-fueled Tehran Research Reactor is considered for conversion to high-density, low-enriched uranium (LEU) fuel. A preliminary neutronics calculation is performed as part of the conversion goal. In this study, two cores are considered: the HEU reference core and a proposed LEU core similar to the reference core, using standardized U3Si2 plates with the option of different 235U loadings. Various possibilities are investigated for the conversion of HEU to LEU fuel elements with 20% enriched 235U loadings of 207 to 297 g 235U/element. For the same equilibrium cycle length, the fuels are compared for flux, power distribution, burnup, and reactivity.