Isotopes of californium Isotopes of californium Californium (Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was Cf in 1950. There are 20 known radioisotopes ranging from Cf to Cf and one nuclear isomer, Cf. The longest-lived isotope is Cf with a half-life of 900 years. Californium-252 (Cf-252) undergoes spontaneous fission and is used in small sized neutron sources. Fission neutrons have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of
Californium Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, started producing small batches of californium in the 1960s. By 1995, the HFIR nominally produced of californium annually. Plutonium supplied by the United Kingdom to the United States under the 1958 US-UK Mutual Defence Agreement was used for californium production. The Atomic Energy Commission sold californium-252 to industrial and academic customers in the early 1970s for $10 per microgram and an average of of californium-252 were shipped each year from 1970 to 1990. Californium metal was first prepared in 1974 by Haire and Baybarz who reduced californium(III) oxide with lanthanum metal