[Chemistry Class Notes] on Cobalt-60 Pdf for Exam

Cobalt is an element present in group 9 of the periodic table. It is a naturally occurring element found in the Earth’s crust in the form of various ores. It is obtained by reductive smelting of its ore to produce a hard, lustrous, and silver-grey metal. The atomic mass of Cobalt is 58.993 and its atomic number is 27. Other than the stable isotope Co59, there are a total of 28 radioactive cobalt isotopes found on earth. 

Most cobalt isotopes have a half-life of less than 1 second and the most stable isotope of Cobalt is Cobalt 60 with a half-life of 5.2713 years. It is a radioactive isotope of Cobalt commonly used in industries and medicines. It is produced artificially in nuclear reactors.

Properties of Cobalt-60

Cobalt 60 is a common source of radiation that emits gamma rays or an accelerator producing beam of electrons. It is produced by nuclear bombardment of stable Cobalt in a nuclear reactor

• Half-Life: half-life is a commonly used term in nuclear physics which depicts the amount of time required for a quantity of element to reduce to half of its initial value. It is essential as it provides information about how quickly unstable atoms undergo radioactive decay and how long they survive.

Cobalt 60 half-life is 5.2713 years which is one of its main advantages being a high-intensity gamma-ray emitter. It has the longest half-life among all the Cobalt isotopes. 

Cobalt mass is 58.993 and the mass of Cobalt isotopes varies from 50u to 73u. Cobalt 60 emits high-intensity gamma rays. The -decayenergy is low and shielded easily while the gamma rays have high energy emission lines around 1.3MeV and are highly penetrating.

The number of Cobalt 60 protons neutrons electrons are 27,33, and 27 respectively.

The radiation from a Cobalt source has been primarily used as a bactericide in the treatment of commodities such as spices, dry fruits, fruits, poultry, onions, and potatoes. The industrial Cobalt-60 is used for phytosanitary applications and medical device sterilization as well. These are operated either continuously or in large batches.

Cobalt Radiotherapy

Cobalt 60 is often the preferred mode of radiation in the treatment of laryngeal cancer. Intensity-modulated radiation therapy or IMRT is being increasingly used in the treatment of advanced diseases in which a linear beam accelerator delivers low-energy photons. There is a concern while using 6-MV photons that they have a larger buildup region and can underdose superficial tissues as most radiation oncology centers have a linear accelerator only. In the absence of cobalt-60, 4-MV photon beams can be used also which are adequate but the concern over 6-MV photons does not compromise treatment and the treatment planning advantages outweigh the small differences in beam properties.

Cobalt-60 Gamma Spectrum

The diagram below depicts the energy and frequency of the gamma radiation emitted by Cobalt-60 to expend the extra energy it possesses. When it undergoes beta-decay it reaches the excited state of Nickel-60.

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Conclusion

Cobalt-60 is the longest living radioactive isotope of Cobalt which is primarily used as a radiation source in irradiation and sterilization processes. But due to increasing costs, other alternatives are also being seen such as E-beam technology which has gained popularity but is not suitable for many products. Gamma rays, E-beam, and X-rays each have their set of advantages and disadvantages when it comes to irradiation modes.