Abstract
The commercial nuclear power industry is investing heavily in advanced fuels that can produce higher power levels with a higher safety margin and be manufactured at low cost. Although chemically stable and inexpensive to manufacture, UO2 fuel is limited by its thermal conductivity. If the fuel thermal conductivity could be increased, existing nuclear reactors would be able to operate at higher powers and new reactors could be designed with higher power densities, thus decreasing the overall cost of electricity and the number of new electrical generating plants needed to meet demand. Movement to higher U-235 enrichments and fuel burnups is limited by UO2 thermal conductivity, which decreases with fuel burnup. Preliminary studies indicate that adding 1% to 5% by volume of long, thin fibers having a high thermal conductivity can substantially increase the bulk thermal conductivity of standard UO2 fuel with minimal decreases in its fissile inventory. The fibers need to remain intact to act as the primary path for transferring heat energy out of the fuel and therefore need to not chemically interact with the UO2 fuel.