Californium

Notable characteristics

Weighable amounts of californium make it possible to determine some of its properties using macroscopic quantities.

²⁵²Cf (2.645-year Bk and most other californium isotopes are made by subjecting berkelium to intense neutron radiation in a nuclear reactor.

Californium has no biological role and only a few californium ion that is stable in aqueous solution is the californium(III) cation.

General uses

The element does have some specialist applications dealing with its radioactivity but otherwise is largely too difficult to produce to have widespread useful significance as a material. Some of its uses are:

• neutron startup source for some nuclear reactors, calibrating instrumentation
• treatment of certain cervical and brain cancers where other radiation therapy is ineffective
• metal fatigue
• airport neutron-activation detectors of explosives
• portable metal detectors^[1]
• neutron moisture gauges used to find water and petroleum layers in oil wells
• portable neutron source in silver prospecting for on-the-spot analysis

In October 2006 it was announced that on three occasions californium-249 atoms had been bombarded with ununoctium (element 118),^[2][3] making this the heaviest element ever synthesized.

Military use

This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)

²⁵¹Cf is famous for having a very small critical mass, high lethality, and short period of toxic environmental irradiation relative to radioactive elements commonly used for radiation explosive weaponry, creating speculation about possible use in pocket nukes. This urban legend is unfounded since it would be very difficult to make a ²⁵¹Cf bomb weighing less than 2 kg, and the costs of such a bomb would be prohibitive. Other weaponry uses, such as showering an area with californium, are not impossible but are seen as inhumane and are subject to inclement weather conditions and porous terrain considerations. Often cited as a consideration is the cost of producing californium in quantity, but the cost citations are usually due to extra fees that laboratory materials companies insert for sake of caution and market needs.

Nuclear fuel cycle

Pertaining to californium's neutron emitter (through spontaneous fission). Hence the concentration of curium and californium among the Minor actinides are important.

History

Californium was transuranium element to be discovered and the team announced their discovery on March 17, 1950. It was named after the U.S. state of California and for the University of California system.

To produce element 98, the team bombarded a microgram-sized target of ²⁴²free neutron.

Due to its $27 million per gram price tag, only 8 grams of ²⁵²Cf have been made in the western world since its discovery by Seaborg in 1950.^{[citation needed]} Plutonium supplied by the United Kingdom to the U.S. under the 1958 US-UK Mutual Defence Agreement was used for californium production.^[4]

Isotopes

Nineteen u (²³⁷Cf) to 256.093 u (²⁵⁶Cf).

Natural occurrence

Although californium does not occur naturally on Earth, the element and its decay products occur elsewhere in the universe. Their electromagnetic emissions are regularly observed in the spectra of supernovae.

References

1. ^ Will you be 'mine'? Physics key to detection. Pacific Northwest National Laboratory (October 25, 2000). Retrieved on 2007-03-21.
2. ^ Sanderson, Katherine (17 October 2006). Heaviest element made - again. nature@news.com. Nature (journal). Retrieved on 2006-10-19.
3. ^ Phil Schewe and Ben Stein (17 October 2006). Elements 116 and 118 Are Discovered. Physics News Update. American Institute of Physics. Retrieved on 2006-10-19.
4. ^ Plutonium and Aldermaston - an historical account. UK Ministry of Defence (4 September 2001). Retrieved on 2007-03-15.

• Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1