Safety Precautions of Cobalt-60
Cobalt-60 sealed sources presents an external Gamma hazard.
Recommended protective clothing when using Cobalt-60: No protective clothing is necessary for work with sealed sources. When working with unsealed sources wear appropriate protective clothing such as laboratory coats, coveralls, gloves, safety glasses/goggles and a suitable mask, if the radioactive material is in the form of dust, power or if it is potentially volatile. Optimizing time, distance and shielding is extremely important. Manipulate sealed sources remotely to minimize extremity doses.
Cobalt-60 usage has always been and continues to be highly regulated at the international, national, regional and local. The international irradiation industry prides itself on an impeccable safety and security record. The industry works closely with regulators to realize continuous improvement in all aspect of the safe manufacture, transportation, use and disposal of cobalt-60 sources. During the 50-year history of the industry, over 800 million curies of cobalt-60 has been safely and securely shipped to gamma processing sites more than 50 countries.
Cobalt-60 must be stored in a position well shielded by lead or uranium. Preferably in a heavily shielded container. Sealed sources pose no internal radiation hazard. However, in the event of loss of containment by the sealed source, all precautions should be taken to prevent inhalation or ingestion of the material. Sealed radioactive sources used in industrial applications should always be within a protective source housing to minimize radiation dose and to protect the source capsule from damage.
Cobalt-60 waste is harder to dispose of because of its radioactivity. However, this does not make it impossible. Since Cobalt-60 has a short half-life compared to other radioactive elements, it decays quickly into Nickel 60 and has a minimal biological and environmental impact.
In 2000 a disused radiotherapy head containing a Cobalt-60 was stored at an unsecured location in Bangkok, Thailand and then accidentally was sold to scrap collectors. Unaware of the dangers, an employee dismantled the head and extracted the source, which remained unprotected for days at the junkyard. Ten people, including the scrap collectors and workers at the junkyard, were exposed to high levels of radiation and became ill. Three of the junkyard workers subsequently died as a result of their exposure.