Improved fuel for nuclear energy

Today’s nuclear reactors run on pellets of uranium dioxide stacked inside fuel rods. The UO₂, although extensively shown to be safe and stable, is not used with full efficiency because its low thermal conductivity causes large temperature gradients. The conductivity decreases further as the fuel burns, which limits a pellet’s operational lifetime. Pellets that can better shed their heat are therefore desirable, and that’s just what nuclear engineers at Purdue University have come up with. Led by Alvin Solomon, the team coated roughly spherical UO₂ granules with a powder of beryllium oxide (BeO), which has a significantly higher thermal conductivity than UO₂. As shown in this cross section, when the coated granules were pressed into pellets, the BeO filled all the available space between the granules. After sintering, the new pellets had a 50% higher thermal conductivity than standard ones. Solomon expects that the new pellets could allow the fuel to produce more power, stay in place longer than the usual three years, and provide the utility companies with greater operational flexibility. The next step is to test the fuel in a reactor. (K. H. Sarma et al. , J. Nucl. Mater. , in press.)