Uranium
A naturally occurring radioactive element used as fuel in nuclear reactors. Natural uranium is 99.3% U-238 and 0.7% U-235. Most reactors require enrichment to 3-5% U-235.
Why It Matters
Uranium fuel has extraordinary energy density — a single fuel pellet the size of a pencil eraser contains the energy of 17,000 cubic feet of natural gas. This is why nuclear plants need refueling only every 18-24 months.
Related Topics
Related Terms
Enrichment
The process of increasing the concentration of uranium-235 (the fissile isotope) in uranium fuel. Most commercial reactors need 3-5% enrichment (natural is 0.7%). Advanced reactors may need HALEU (5-20%).
Nuclear Fission
The process of splitting a heavy atomic nucleus (such as uranium-235 or plutonium-239) into two lighter nuclei, releasing a large amount of energy. This is the reaction that powers all current nuclear power plants.