Periodic Table -> Californium


Californium Details

Californium Symbol: Cf

Californium Atomic Number: 98

Californium Atomic Weight: (251)

What is Californium?

Californium (atomic number 98, symbol Cf) is a radioactive element from the actinide series, named after the University of California and California. It is a grey or silvery white metal, and its density is greater than the density of lead. Californium does not occur in nature, and particle accelerators and nuclear reactors are used for its production. Californium is also a byproduct of the production of plutonium and different radioactive decay and neuron capture routes. Californium-249, an isotope of californium, occurs with beta decay of berkelium-249 and the high-numbered or heavier isotopes are typically produced in nuclear reactors, using intense neutron irradiation. Californium-251 is the most stable isotope of californium, and its half-life is 898 years. Given this short half-life, the isotope does not occur in the earth’s crust. The most common isotope of californium used is californium-252. It is produced in Russia’s Research Institute of Atomic Reactors and the US Oak Ridge National Laboratory. While californium has not been detected in nature so far, small amounts of the metal may be found in some of the uranium ores. Some have suggested that californium can occur with stellar explosions, but this has not been confirmed.

Californium was produced in laboratory conditions using helium ions or alpha particles to bombard curium. The element was discovered at the University of California in 1950. Given its radioactivity, californium is a health hazard only if it enters the body. Risk, however, is associated with californium-251 and californium-249 which emit gamma rays. The main sources of exposure are water and food that contain isotopes of californium as well as breathing in californium-contaminated dust. Given that californium enters the body more easily when inhaled, as opposed to ingested, the two routes of exposure can prove important. Cancer is a major health concern, which can result with californium isotopes emitting ionizing radiation. It can be deposited in the liver and on bone surfaces.

Under pressure below or above 900 °C (normal pressure), there are 2 crystalline forms of the element, with a third one existing at high pressure. At room temperature, the element will tarnish slowly in air.

There are different applications of this chemical and its isotopes. Californium-252 is a neutron emitter, making californium a non-reactor based or portable neutron source, which used for the analysis of neutron activation, as well as a neutron start-up source in some types of nuclear reactors. Analysis of neutron activation helps detect the level of elements in different samples. Californium neutrons are also used to treat some brain cancers and cervical cancers for which radiation therapy proves ineffective. Californium is also used with bulk material analyzers and elemental coal analyzers in the cement and coal industries. The ability of californium’s neutrons to penetrate into materials has been used in aircraft neutron radiology, weapon components used to detect trapped moisture, cracks, bad welds, and corrosion, fuel rod scanners and other detection instruments, as well as in portable metal detectors. Californium-252 is used in neutron moisture gauges as to detect petroleum and water layers in oil wells. These are also used as a neutron source in on-the-spot-analysis for silver and gold prospecting. Finally, these are also used to detect movement of ground water. Californium-252 has been mostly used for fuel rod scanning, neutron radiography, reactor start-up, and activation analysis.

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