RadioisotopesMedical Treatment:

Co-60 is used for cancer treatment by irradiating the affected areas of the body with gamma rays, which kill cancer cells (and some normal cells too). Co-60 is made by neutron bombardment of normal Co-59; it disintegrates by beta emission to form Ni-60. It is the gamma rays that are produced by this decay that attack cancer because they are able to penetrate deeply into body tissue.

Co-60 is used because the gamma rays carry a suitable amount of energy to destroy certain biological

molecules, and because Co-60 has a suitable half-life (5.27 years). This half-life is sufficiently long enough for the radiation source to have a reasonable shelf life in equipment (about 4 to 6 years) but short enough for the source to emit a reasonable intensity of radiation.

Unwanted beta particles can be filtered out. The gamma rays are constant and allows for accuracy. Co-60 is relatively cheap and easy to manufacture. Gamma rays are directed only to the specific targeted part of the body, where it destroys DNA in carcinoma and thus reduces or eradicates their reproduction and existence.

Industry Uses:

Co-60 is used in industry as a thickness gauge because it has a fairly low energy emission but a long half-life. It is beneficial to have low energy so that a significant proportion of radiation is absorbed by the thin film, and has a long half-life to reduce the frequency that the source must be replaced.

Co-60 is used in irradiation of medical supplies and food due to the gamma rays effectiveness of destroying large biological molecules such as DNA, so that bacteria are killed to sterilise medical supplies such as dressings and bandages. It also is effective in destroying microorganisms to minimise soilage and extend self-life. Food irradiation requires gamma rays of sufficient energy to destroy bacteria but not enough energy to make the food radioactive. Co-60 is suitable for this purpose.

Co-60 is not very harmful once disposed, and it has the ideal intensity to destroy what is required without making the subject radioactive. Gamma radiation breaks chemical bonds and ionises particles, damages DNA,

slows ripening, sprouting, spoilage and kills some bugs. It can however create some new unknown chemicals in food, it destroys thiamine, some foods are unsuitable and negligence can cause excess exposure.

Reaction Mechanisms in Research

I-131 can be used to study equilibrium in H2 (g) + I2 (g) ⇌ 2HI (g)

C-14 can be used to work out the individual steps that occur in photosynthesis, by exposing a plant to carbon dioxide containing some C-14. By isolating particular compounds at various stages of the process and measuring their radioactivity, they could determine whether the compound came from the carbon dioxide or not. This is how the mechanism for photosynthesis was determined. This is called using C-14 as a tracer.