Plutonium-239 is a radioactive isotope of plutonium, primarily used as fuel in nuclear reactors and in the production of nuclear weapons. It has a half-life of about 24,100 years, meaning it takes that long for half of a sample to decay. This long half-life makes it a significant concern for nuclear waste management. Discovered in 1940, Plutonium-239 is produced through the irradiation of uranium-238 in nuclear reactors. Its ability to sustain a nuclear chain reaction makes it valuable for both energy generation and military applications. However, its radioactivity poses health risks, necessitating strict safety measures in handling and storage.