Californium - Production

Production

Californium is produced in nuclear reactors and particle accelerators. Californium-250 is made by bombarding berkelium-249 (249
97Bk) with neutrons, forming berkelium-250 (250
97Bk) via neutron capture (n,γ) which, in turn, quickly beta decays (β−) to californium-250 (250
98Cf) in the following reaction:

249
97Bk(n,γ)250
97Bk → 250
98Cf + β−

Bombardment of californium-250 with neutrons produces californium-251 and californium-252.

Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of californium-252 and microgram amounts of californium-249. As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce primarily californium-252 with lesser amounts of isotopes 249 to 255.

Microgram quantities of californium-252 are available for commercial use through the U.S. Nuclear Regulatory Commission. Only two sites produce californium-252 – the Oak Ridge National Laboratory in the United States, and the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. As of 2003, the two sites produce 0.25 grams and 0.025 grams of californium-252 per year, respectively.

Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. Californium-253 is at the end of a production chain that starts with uranium-238, includes several isotopes of plutonium, americium, curium, berkelium, and the californium isotopes 249 to 253 (see diagram).