Isotopes of cobalt

== Stellar nucleosynthesis of cobalt-56 ==

One of the terminal nuclear reactions in stars prior to supernova produces Ni. Ni then decays to Co, which then decays to Fe. These decays power the luminosity displayed in light decay curves. Both the light decay and radioactive decay curves are expected to be exponential. Therefore, the light decay curve should give an indication of the nuclear reactions powering it. This has been confirmed by observation of bolometric light decay curves for SN 1987A. Between 600 and 800 days after SN1987A occurred, the bolometric light curve decreased at an exponential rate with half-life values from 68.6 days to 69.6 days. The rate at which the luminosity decreased closely matched that expected of exponential decay of Co. == Cobalt-57 ==

Cobalt-57 (Co or Co-57) is used in medical tests; it is used as a radiolabel for vitamin B uptake. It is useful for the Schilling test. Co is used as a source of gamma rays in Mössbauer spectroscopy of iron-containing samples. Electron capture by Co forms an excited state of the Fe nucleus, which in turn decays to the ground state with the emission of a gamma ray. Measurement of the gamma-ray spectrum provides information about the chemical state of the iron atom in the sample. == Cobalt-60 ==

Cobalt-60 (Co or Co-60) is used in radiotherapy. It produces two gamma rays with energies of 1.17 MeV and 1.33 MeV. The Co source is about 2 cm in diameter and as a result produces a geometric penumbra, making the edge of the radiation field fuzzy. The metal has the unfortunate habit of producing fine dust, causing problems with radiation protection. The Co source is useful for about 5 years but even after this point is still very radioactive, and so cobalt machines have fallen from favor in the Western world where linacs are more usual. Cobalt-60 (Co) is useful as an industrial gamma ray source also: uses for industrial cobalt include • Sterilization of medical supplies and medical waste • Radiation treatment of foods for sterilization (cold pasteurization) • Industrial radiography (e.g., weld integrity radiographs) • Density measurements (e.g., concrete density measurements) • Tank fill height switches == See also ==