* Nuclear reactors: Plutonium-239 is the most common isotope of plutonium used in nuclear reactors. It is used as a fuel in both thermal and fast neutron reactors.

* Nuclear weapons: Plutonium-239 is also used in the production of nuclear weapons. It is the primary fissile material in atomic bombs.

* Radioisotope thermoelectric generators (RTGs): Plutonium-238 is used as a heat source in RTGs. RTGs are used to provide electrical power for spacecraft, satellites, and other remote applications.

* Medical applications: Plutonium-238 is also used in some medical applications, such as the production of radiopharmaceuticals and the treatment of cancer.