60Co

Cobalt-60 (60Co) is a radioactive isotope of cobalt with atomic number 27 and a mass number of 60. It is not stable and decays by beta minus emission to nickel-60, with a half-life of about 5.27 years. The decay process releases two principal gamma rays with energies of approximately 1.17 MeV and 1.33 MeV, making 60Co a strong source of penetrating gamma radiation.

60Co does not occur naturally in meaningful quantities; it is produced in nuclear reactors by neutron irradiation of stable cobalt-59 via the reaction 59Co(n,γ)60Co. The resulting 60Co is typically encapsulated as a sealed source for use in radiation devices, where strict containment and shielding are essential to protect workers and the public.

Because of its high-energy gamma emissions and a practical half-life, 60Co has been widely used in radiotherapy and industry. In medical radiotherapy, cobalt-60 teletherapy units deliver external beam radiation for cancer treatment. In industry, sealed 60Co sources are employed for non-destructive testing such as radiography, material analysis, and the sterilization of medical equipment and some food products. Although newer technologies have supplanted some uses, 60Co remains common in certain applications due to the penetration and reliability of its gamma rays.

Safety and regulatory considerations are central to 60Co handling. Sealed sources require robust shielding, typically lead or heavy concrete, and careful source containment to prevent leakage or accidental exposure. Regulations govern procurement, use, transport, storage, and disposal to minimize external and potential internal exposure, environmental release, and security risks.