High-Efficiency Uranium Dioxide Composite Fuel Pellet that is Less Expensive and Cooler-Running in Nuclear Reactors

Increases Reactor Output and Shortens Fuel Cooling Times

This uranium dioxide composite fuel pellet, which boasts improved thermal conductivity, will extend the life of UO2 fuel within nuclear reactors to save money and enhance safety. Radioactive crystalline powder uranium dioxide (UO2) is a naturally occurring substance and the most commonly used material in nuclear reactors' fuel rods. UO2 has a high melting point, good high-temperature stability, chemical compatibility with cladding and coolant, and resistance to radiation. Its main disadvantage is its low thermal conductivity, which can cause large temperature gradients in UO2 fuel pellets. These temperature gradients produce thermal stresses that can lead to extensive fuel pellet cracking, an increased rate of fission gas release, more fission gas bubbles and fuel pellet swelling - issues that limit UO2 fuel's life within reactors. Using conventional pellet processing techniques, it is not possible to obtain high density UO2/SiC composite pellets. Researchers at the University of Florida have employed unique spark plasma sintering to develop an inexpensive high-density urania/SiC composite with enhanced thermal conductivity. This cooler-running nuclear fuel pellet will increase reactor output, save money and enhance safety.

Application

Uranium dioxide composite fuel pellet with high density and thermal conductivity for nuclear reactors

Advantages

• Decreases the amount of heat stored in the fuel, allowing for faster cooling at shutdown or loss-of-coolant accidents
• Enables higher thermal conductivity and density with dopants, increasing reactor output
• Produces greatly reduced fuel temperatures with resultant decreases in thermal stress, thermal expansion, thermal cracking, and fission gas release, making it safer than available fuel
• Extends the life of UO2 fuel, saving money

Technology

University of Florida researchers have developed a high-density nuclear fuel pellet with increased conductivity and a technology that rapidly sinters powder to create the pellet. The researchers' spark plasma sintering (SPS) technique, essential for manufacturing the fuel pellet, uses significantly lower processing temperatures and much shorter processing times to combine a highly conductive material with uranium dioxide (UO2). The result is a dense pellet with excellent thermal conductivity. Examples of thermally conductive starting materials include silicon carbide (SiC) and diamond.