鈾 (uranium) is a heavy, silvery-white metal that is primarily used as fuel in nuclear reactors. It is a naturally occurring element found in the Earth's crust and is known for its radioactive properties. Uranium is essential for generating nuclear energy, which is a significant source of electricity in many countries. In addition to its use in energy production, uranium is also utilized in the manufacturing of nuclear weapons. The element has several isotopes, with U-235 being the most commonly used for fission reactions. Due to its radioactivity, uranium must be handled with care to ensure safety and minimize environmental impact.