Cobalt-60

Cobalt-60, 60
Co
, is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisotopic and mononuclidic cobalt isotope 59
Co
. 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 (in the absence of added cobalt) the incidentally produced 60
Co
is largely the result of multiple stages of neutron activation of iron isotopes in the reactor's steel structures via the creation of 59
Co
precursor. The simplest case of the latter would result from the activation of 58
Fe
. 60
Co
decays by beta decay to the stable isotope nickel-60 (60
Ni
). The activated nickel nucleus emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear equation of the reaction is 59
27Co
+ n → 60
27Co
→ 60
28Ni
+ e⁻ +
ν
e + gamma rays.

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