Isotopes of Cobalt

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. 

  • Isotopes: Isotopes are elements with the same number of protons but they differ in the number of neutrons. All isotopes of an element have the same atomic number but different atomic mass. 

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.

[Image will be Uploaded Soon]


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. 

FAQs (Frequently Asked Questions)

Question 1: What are the Various Advantages of Cobalt 60 Over X-Ray or Radium?

Ans- Cobalt 60 is a radioactive isotope of Cobalt obtained upon irradiating the stable isotope cobalt-59 with neutrons in a nuclear reactor. It is the longest living radioactive Cobalt isotope with a half-life of 5.2714 years. Cobalt is used in place of X-ray or radium during the inspection of materials to reveal the internal structure, flaws, or any foreign objects for various reasons. 

  • Cobalt 60 is much more economical and less expensive than radium and has more homogenous gamma radiation.

  • It also has softer beta radiation which is helpful as it is easy to filter out in the absence of any contamination. 

  • The physical properties of Cobalt 60 allow it to be shaped in any form to meet special requirements.

  • Due to resistance to bulk oxidation and low solubility in water, it has some safety advantages over other gamma sources as well.

Question 2: Write Down the Various  Cobalt 60 Uses.

Ans- Cobalt 60 is commonly used as a gamma source because it can be produced in predictable quantities and has high radioactivity by exposing natural cobalt to neutrons in the reactor. The various medical and industrial Cobalt 60 uses are as follows:

Medical Uses

  • Cobalt 60 is used in cancer therapy and as a radioactive tracer in biology.

  • It is also used in the process of radiotherapy.

  • It is also used to sterilize medical supplies and medical waste.

  • It is a source of radiation for food irradiation.

Industrial Uses

  • Cobalt 60 is commonly used in industrial radiography.

  • It is used in the measurement of density.

  • It is also used in tank fill switches.

  • It is used in the radiation treatment of foods for sterilization.

  • It is used as a radiation source in leveling devices and thickness gauges.