Pu-239

Plutonium-239 (Pu-239) is a radioactive isotope of plutonium with a half-life of approximately 24,100 years. It undergoes alpha decay, emitting alpha particles and transforming into uranium-235 (U-235). Pu-239 is notable for being fissile, meaning it can sustain a nuclear chain reaction. This property makes it highly valuable in nuclear energy and weapons applications. Pu-239 is produced artificially in nuclear reactors when uranium-238 absorbs a neutron.

Reactor-grade, unrefined plutonium-239 also contains other plutonium isotopes (Pu-238, Pu-240, Pu-241, etc.). As a result, americium-241 begins to accumulate in reactor-grade plutonium due to the decay of plutonium-241, emitting a significant amount of gamma radiation. The gamma spectrum of americium-241 closely resembles that of plutonium-239, making it challenging to definitively identify the presence of plutonium-239 in spectral analysis. The accumulation of decay products from plutonium isotopes introduces additional properties to the fuel and degrades its quality, thereby limiting its service life, after which purification is required. Plutonium isotopes and their decay products emit alpha, beta particles, and gamma radiation.

Pu-239 is primarily used in nuclear reactors and nuclear weapons. In reactors, it acts as a fuel in fast breeder reactors, where it contributes to the production of energy and the generation of additional fissile material. In nuclear weapons, Pu-239 is the primary fissile material due to its ability to undergo a rapid chain reaction. It has also been used in scientific research to study nuclear properties and processes.

Pu-239 does not occur naturally in significant quantities and is produced in nuclear reactors through neutron capture by uranium-238. It is found in spent nuclear fuel and reprocessing facilities where nuclear material is recycled. Trace amounts of Pu-239 are present in the environment as a result of atmospheric nuclear weapons testing and nuclear accidents. Its handling and use are strictly controlled due to its radiological and proliferation risks.