Californium

Californium is a radioactive chemical element with the symbol Cf and atomic number 98. It is a member of the actinide series and has no stable isotopes. Californium was first synthesized in 1950 at the University of California, Berkeley, by Glenn T. Seaborg, Stanley G. Thompson, Albert Ghiorso, and coworkers. The element was named after the state of California.

As a heavy actinide, californium metal is a dense, silvery material that is highly radioactive. It does not occur naturally and is produced in nuclear reactors or particle accelerators. In aqueous solution, californium most commonly exhibits +3 oxidation state, with +4 and other oxidation states encountered under certain conditions. All isotopes of californium are radioactive, and some isotopes, notably californium-252, are known for spontaneous fission, which makes them useful as neutron sources.

Most californium used commercially is californium-252, produced in reactors by neutron irradiation of curium and subsequent beta decays. Cf-252 emits neutrons and gamma radiation, enabling it to serve as a compact, intense neutron source. Other californium isotopes are produced in smaller quantities for research purposes.

Applications of californium include neutron sources for neutron activation analysis, neutron radiography, and the initiation of nuclear reactors in some startup procedures. It has also been used in medical research and in specialized industrial instrumentation. Safety concerns are significant due to its intense radioactivity; handling requires remote manipulation, shielding, and strict regulatory controls to prevent radiation exposure.