Californium

Californium was first made in 1950 at Berkeley by Stanley Thompson, Kenneth Street, Albert Ghiorso and Glenn Seaborg, by bombarding curium with alpha particles. It was named after the state and university of California. Californium is a silvery, radioactive metal and a prodigious emitter of neutrons, a property that gives it real practical uses in starting nuclear reactors, in detecting gold and oil in boreholes, and in a form of cancer radiotherapy. A single microgram of californium-252 is an intense neutron source, so that this vanishingly rare, laboratory-born metal earns a genuine place in industry and medicine, and it also serves as a target for attempts to synthesise still heavier elements.

A single gram of californium-252 has been priced at tens of millions of dollars, making it among the most valuable materials by weight ever produced, though in practice only microgram quantities are made at a time. Its intense, steady stream of neutrons is used to activate oil-bearing rock in borehole logging, revealing the presence of hydrocarbons and moisture from the pattern of radiation the rock reflects back. The same neutron-rich property also makes small californium sources useful for starting up nuclear reactors, providing a reliable initial burst of neutrons to begin the chain reaction cleanly.

Californium honours the state of California and its university at Berkeley, where it and its predecessors were created; the discoverers noted wryly that, unlike the earlier place-named elements, it had not been necessary to cross an ocean to find a new element, only to build one at home. Its name completed a small cluster of geographic tributes, berkelium and californium, to the place that had produced most of the transuranium elements. Californium has no ancient or esoteric tradition, being a synthetic creation of 1950, but it is among the most practically useful of the exotic heavy elements: a single microgram is an intense neutron source, so that this vanishingly rare, laboratory-born metal earns its keep in industry and medicine far beyond the small circle of nuclear science.

Only a handful of grams of californium-252 are believed to exist in the world at any given time, manufactured almost exclusively at Oak Ridge National Laboratory in the United States and at a sister facility in Russia, the only two sites equipped for the sustained reactor irradiation the element's production demands. That scarcity, more than any chemical property, is what keeps californium's price so extraordinarily high relative to almost any other material on Earth.