The objective of this work is to make a preliminary reactivity analysis of an original design of a fuel rod with biconcave cross section. In this phase of the project, reactivity sensitivity tests were carried out through the subchannel area, considering UO2 fuel enriched at 4% and 5%, for the fuel temperatures of 600K and 900K. We observed that the best area ranges were the regions from 7.5 to 7.9 cm2 for the UO2 enrichment of 5% and from 6.2 to 6.6 cm2 for the UO2 enrichment of 4%. The next step will be a study of the fuel temperature coefficient.