Noun
californium-252 (uncountable)
(physics) An isotope of californium, 98Cf, with a half-life of 2.6 years; it is popular as a source of neutrons.
Californium-252, with a half-life of about 2.64 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia. Source: Internet