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The main advantage of 60 Co is that it is a high-intensity gamma-ray emitter with a relatively long half-life, 5.27 years, compared to other gamma ray sources of similar intensity. The β-decay energy is low and easily shielded; however, the gamma-ray emission lines have energies around 1.3 MeV, and are highly penetrating.
Decay scheme of 60 Co. These relations can be quite complicated; a simple case is shown here: the decay scheme of the radioactive cobalt isotope cobalt-60. [1] 60 Co decays by emitting an electron with a half-life of 5.272 years into an excited state of 60 Ni, which then decays very fast to the ground state of 60 Ni, via two gamma decays.
In addition to their uses in radiography, both cobalt-60 (60 Co) and iridium-192 (192 Ir) are used in the radiotherapy of cancer. Cobalt-60 tends to be used in teletherapy units as a higher photon energy alternative to caesium-137, while iridium-192 tends to be used in a different mode of therapy, internal radiotherapy or brachytherapy.
For technetium-98 and heavier isotopes, the primary mode is beta emission (the emission of an electron or positron), producing ruthenium (Z = 44), with the exception that technetium-100 can decay both by beta emission and electron capture. [59] [60] Technetium also has numerous nuclear isomers, which are isotopes with one or more excited nucleons.
Radioactive decay scheme of 60 Co Gamma emission spectrum of cobalt-60. One example of gamma ray production due to radionuclide decay is the decay scheme for cobalt-60, as illustrated in the accompanying diagram. First, 60 Co decays to excited 60 Ni by beta decay emission of an electron of 0.31 MeV. Then the excited 60 Ni
Cobalt-60 (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 60 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 ...
Beta decay of fission products of mass 95–98 stops at the stable isotopes of molybdenum of those masses and does not reach technetium. For mass 100 and greater, the technetium isotopes of those masses are very short-lived and quickly beta decay to isotopes of ruthenium. Therefore, the technetium in spent nuclear fuel is practically all 99 Tc.
The deposited cobalt-60 would have a half-life of 5.27 years, decaying into 60 Ni and emitting two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear equation of the reaction is: 59 27 Co + n → 60 27 Co → 60 28 Ni + e − + gamma rays. Nickel-60 is a stable isotope and undergoes no further decays after the ...