Uranium-238 is a naturally occurring isotope of uranium, making up about 99.3% of all uranium found in nature. It has a long half-life of approximately 4.5 billion years, which means it decays very slowly. This isotope is not directly usable as fuel in most nuclear reactors, but it can be converted into Plutonium-239, a fissile material used in nuclear energy and weapons. Uranium-238 is primarily mined from uranium ore and is often used in the production of nuclear fuel. It also plays a role in the process of radiometric dating, helping scientists determine the age of rocks and fossils. Its stability and abundance make it an important element in both energy production and scientific research.