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.
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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.
FAQs on Cobalt-60
1. What exactly is Cobalt-60?
Cobalt-60 (Co-60) is a synthetic radioactive isotope of the element cobalt. It is not found in nature and is created artificially in nuclear reactors by bombarding the stable isotope, cobalt-59, with neutrons. It is highly valued for the powerful gamma radiation it emits.
2. What are the most common uses of Cobalt-60 in medicine and industry?
Cobalt-60 has several important applications due to its strong gamma ray emission. The main uses are:
- Medical Uses: It is used in radiotherapy to treat cancer (often called the 'cobalt bomb'), to sterilise medical equipment like syringes and gloves, and to sterilise blood for transfusions.
- Industrial Uses: It is used in industrial radiography to inspect metal parts and welds for flaws, for food irradiation to kill bacteria and prolong shelf life, and in gauges that measure the thickness of materials.
3. How many protons, neutrons, and electrons are in a neutral Cobalt-60 atom?
A neutral atom of Cobalt-60 contains:
- 27 protons, as the atomic number of cobalt is 27.
- 27 electrons, to balance the positive charge of the protons in a neutral atom.
- 33 neutrons, which is calculated by subtracting the atomic number (27) from the mass number (60).
4. Why is Cobalt-60 often preferred over other radiation sources like radium for certain applications?
Cobalt-60 has several advantages over sources like radium. It is much more cost-effective to produce. The gamma rays it emits are of a more uniform energy, which is better for applications like cancer therapy. Furthermore, it can be shaped into various forms for specific industrial needs, and it has safety advantages due to its low solubility in water and resistance to oxidation.
5. How does the radiation from Cobalt-60 help in sterilising medical equipment?
The process is called irradiation. The high-energy gamma rays emitted by Cobalt-60 can pass through sealed packaging and kill harmful microorganisms like bacteria, viruses, and moulds by damaging their DNA and cellular structure. This is an effective method for sterilising heat-sensitive items, such as plastic syringes or gloves, that would be damaged by steam sterilisation.
6. What is the significance of Cobalt-60's half-life for its practical use?
Cobalt-60 has a half-life of 5.27 years. This is a key reason for its usefulness. This duration is long enough for a Cobalt-60 source to be used effectively for several years in medical or industrial equipment without needing frequent replacement. However, it is also short enough that the source is highly radioactive and powerful enough for its intended applications, like therapy and sterilisation.
7. What makes Cobalt-60 potentially dangerous and how is it handled safely?
The danger of Cobalt-60 comes from its intense gamma radiation, which can penetrate the body and damage living cells, leading to radiation sickness or an increased risk of cancer. Due to this risk, Cobalt-60 must be handled with extreme care. It is always kept inside heavily shielded containers, usually made of lead or concrete, to block the radiation. It is typically manipulated using remote-controlled robotic arms to ensure no direct human exposure.
