Californium

BeschreibungCalifornium does not occur in nature. The element was synthesized in 1949 at the Lawrence Berkeley Laboratory in Berkeley, California by Thompson, Ghiorso and Seaborg (Thompson, S.G., Ghiorso, A. and G. T. Seaborg. 1950. Phys. Rev., 77, 838). It has 12 isotopes. It is the fifth man-made transuranium element. Presently, the element has no commercial application.

OccurrenceNeither californium nor its compounds are found in nature. All of its isotopes are producedartificially in extremely small amounts, and all of them are extremely radioactive. All of itsisotopes are produced by the transmutation from other elements such as berkelium and americium.Following is the nuclear reaction that transmutates californium-250 into californium-252: 250Cf + (neutron and λ gamma rays) → 251Cf + (neutron and λ gamma rays) → 252Cf.

VerwendenCalifornium’s uses are limited, which is why the U.S. Nuclear Regulatory Commission,which controls the output and use of radioisotopes, has made californium-252 available forcommercial use at the cost of only $10 per millionth of a gram. This small quantity is adequatefor many sources of free neutrons to be used commercially. For example, free neutrons can be used in devices to measure moisture in products, including the Earth’s crust, to find wateror supplies of underground oil. Cf-252’s ability to produce neutrons has also found uses inmedicine. Cf-252’s natural spontaneous fission makes it an ideal and accurate counter forelectronic systems.

synthetischeAll isotopes of the element are synthesized in the nuclear reactor. The first isotope synthesized had the mass 241, produced by irradiation of milligram quantities of americium-241 with alpha particles of 35 MeV in a cyclotron: The product was separated by ion exchange While the lighter isotopes are prepared by alpha particle bombardment, the heavier ones by neutron irradiation of large quantities of americium, curium or plutonium: Only a small fraction of Bk-249 is obtained by the above reaction because neutrons also induce fission. Alternatively, uranium-238 may be converted to Bk-249 by very short but intense neutron bombardment followed by five successive beta decays.