Plutonium

Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal, silvery in appearance and highly reactive with air when finely divided. It has multiple allotropes and exists in several oxidation states, commonly +3 to +7. It forms oxides such as PuO2 that are very stable.

Natural occurrence: trace amounts in uranium-bearing ores but not economically recoverable; most plutonium is produced artificially in nuclear reactors by irradiating uranium-238 and subsequently chemically separating the plutonium.

Isotopes: The most important fissile isotope is Pu-239, produced from U-238 and with a long half-life of about 24,000 years. Other notable isotopes include Pu-238 (half-life ~87.7 years), Pu-240 (several thousand years) and Pu-241 (about 14 years), with varying radiotoxicity and emission.

Uses: Pu-239 is used as a fissile material in some nuclear weapons and in mixed oxide (MOX) reactor fuel. Pu-238 provides heat in radioisotope thermoelectric generators for space missions. Plutonium has been used in naval reactors and in research contexts. Reprocessing spent fuel and recycling plutonium is common in some nuclear programs.

Safety and regulation: Plutonium is highly radiotoxic and chemically dangerous, emitting alpha radiation; inhalation or ingestion is the primary risk. Handling requires specialized facilities, containment, and monitoring. International frameworks such as the IAEA and the Nuclear Non-Proliferation Treaty govern its use and transport, and long-term management focuses on secure storage and waste isolation.

History: Discovered in 1940 at the University of California, Berkeley, by Seaborg, McMillan, Kennedy, and Wahl, and named after the planet Pluto.