Information on the radioisotope: Cobalt 60 used in medicine and in industry

Radioactive decay, Radionuclide, Industrial radiography

a) Identify a radioisotope that is used in medicine or industry and briefly outline its use

Cobalt-60 is used in industrial radiography to inspect metal parts and welds for defects, in gamma sterilisation of equipment and in gauging. In the area of medicine, Cobalt-60 is used in cancer radiotherapy.

b) Describe how the radioisotope is made.

Radioactive cobalt-60 is produced in a process called activation, when materials in reactors, such as steel, are exposed to neutron radiation. Often isolated neutrons collide into atoms, and because they have no charge there is no repulsive force against them. These neutrons turn the atoms into isotopes; in this case typical iron-56 becomes iron-57, 58 and then 59. The heavy iron-59 atom is very unstable and decays to cobalt-59. Then cobalt-59 captures a neutron and becomes cobalt-60, which is very unstable and decays into nickel 60.

c) How does the radioisotope decay and state its half-life.

Cobalt-60 undergoes radioactive decay with the emission of beta particles and strong gamma radiation. It ultimately decays to non-radioactive nickel with a half-life of 5.24 years.

d) Identify those properties of the radioisotopes that make it suitable for the use outlined above.

Cobalt-60 can be used in a chemically inert form held inside a sealed container. This enables the equipment to have a long lifetime and not require regular maintenance.

In gamma radiation, beams of radiation are used to penetrate engines, welded joints, and metal casing to show flaws in the metal. Photographic plates are used to show up where the flaws are. Radioactive material such as cobalt-60 is placed in a sealed titanium capsule, which still allows gamma radiation to penetrate. The ease of transportation and since no power is needed means it is useful in remote places to check on natural gas or oil pipelines.

With a half-life of 5.24 years and being a strong emitter of gamma radiation, cobalt-60 is used to sterilise medical...
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