solid ceramic uranium fuel pellets

Nuclear power plants don't burn fuel in the conventional sense

The difference between a nuclear power plant and a fossil-fuel power plant is the heat source. A fossil-fueled plant burns fuel — such as coal, oil or gas — to create steam that spins a turbine to generate electricity.  

Nuclear power plants split uranium atoms inside a reactor in a process called fission to produce steam that spins a turbine to generate electricity. Fission produces no carbon dioxide.

Uranium fuel comes to the power plant in the form of small, solid ceramic pellets. When it arrives, it is not radioactive and is thoroughly inspected by well-trained engineers to ensure it is in safe condition. The electricity produced by one fuel pellet, roughly the size of a pencil eraser, is equal to the amount produced by 4.5 barrels of oil, 17,000 cubic feet of natural gas or one ton of coal.

Inside the reactor, pellets of uranium are stacked end-to-end in 12-foot long tubes, or fuel assemblies. These fuel assemblies are precisely arranged in bundles within the reactor with spaces between the bundles for control rods.  The control rods can be moved in and out of the reactor to stop and start the fission process.

Fermi 2 contains 185 control rods and 764 zirconium alloy fuel assemblies.  Each assembly contains approximately 13,000 uranium pellets.