A uranium oxide fuel pellet having an inner region and an outer rim region about the inner region, and that the fuel pellet is cylindrical and the inner region and outer rim region are coaxial cylindrical regions. The outer rim region has an excess of oxygen in comparison to the inner region, wherein high burnup structure (HBS) formation will be suppressed or delayed. Preferably, the excess oxygen is obtained by a chemical treatment by immersing the pellet in hydrogen peroxide (H2O2) or potassium permanganate (KMnO4) in solution.