cobalt-60

thumb|right|γ-ray spectrum of cobalt-60

Cobalt-60 (Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors through neutron activation of (of which natural cobalt consists entirely). Measurable quantities are also produced as a by-product of typical nuclear power plant operation and may be detected externally when leaks occur. In the latter case, the incidentally produced is largely the result of multiple stages of neutron activation of iron isotopes in the reactor's steel structures via the creation of its precursor. The simplest case of the latter would result from the activation of . undergoes beta decay to an excited state of the stable isotope nickel-60 (), which then emits two gamma rays with energies of and . The overall equation of the nuclear reaction (activation and decay) is: + n → → + e + + 2γ