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Physics

Nuclear Energy

Nuclear Energy

The protons and neutrons (nucleons) in the nucleus of each atom are held together by very powerful nuclear forces. An enormous amount of energy is therefore required to tear the nucleon apart. This energy is over 106 times more than that required to remove the electrons from an atom.

Nuclear Fusions

Fusion is a nuclear process in which two or more light nuclei combine or fuse to form a heavier nucleus with the release of a large amount of energy.

A typical example of nuclear fusion is the fusion of two hydrogen nuclei to form Helium, He.

21H       +       31H        →         42He   +     10n      +       Energy

↑                       ↑                     ↑                 ↑

Deuterium     tritium         Helium           neutron

In the above fusion process the two isotopes of hydrogen, deuterium and tritium, combine to form the heavier nucleus of Helium. To bring the two light nuclei together in a fusion process, very high temperature of the order of 106 – 10degrees Celcius are required to over-come the coulomb repulsive forces between the two nuclei. This poses severe technological problem due to the fact that materials to withstand this high temperature are difficult to come by. It is for this reason that fusion reactions have not been harnessed in nuclear power stations on Earth to produce power, even though they theoretically offer the prospect of enormous quantities of cheap power.

The sun and stars produce an enormous output of energy through nuclear fusion. This is because of the presence of hydrogen isotope in the sun and the conditions of extremely high temperature and pressure are found in the interior of the sun and stars.

Nuclear Energy

The protons and neutrons (nucleons) in the nucleus of each atom are held together by very powerful nuclear forces. An enormous amount of energy is therefore required to tear the nucleon apart. This energy is over 106 times more than that required to remove the electrons from an atom.

Nuclear Fusions

Fusion is a nuclear process in which two or more light nuclei combine or fuse to form a heavier nucleus with the release of a large amount of energy.

A typical example of nuclear fusion is the fusion of two hydrogen nuclei to form Helium, He.

21H       +       31H        →         42He   +     10n      +       Energy

↑                       ↑                     ↑                 ↑

Deuterium     tritium         Helium           neutron

In the above fusion process the two isotopes of hydrogen, deuterium and tritium, combine to form the heavier nucleus of Helium. To bring the two light nuclei together in a fusion process, very high temperature of the order of 106 – 10degrees Celcius are required to over-come the coulomb repulsive forces between the two nuclei. This poses severe technological problem due to the fact that materials to withstand this high temperature are difficult to come by. It is for this reason that fusion reactions have not been harnessed in nuclear power stations on Earth to produce power, even though they theoretically offer the prospect of enormous quantities of cheap power.

The sun and stars produce an enormous output of energy through nuclear fusion. This is because of the presence of hydrogen isotope in the sun and the conditions of extremely high temperature and pressure are found in the interior of the sun and stars.

Advantages of Fusion over Fission

  1. Fusion is more easily achieved with lightest elements such as hydrogen; nuclear repulsion is easily overcome as nuclei approach each other.
  2. The draw materials required for fusion are more cheaply and readily available. For example, hydrogen can be obtained by the electrolysis of sea water which is cheap and in plentiful supply.
  3. Fusion process produces less dangerous (i.e. non radioactive) by-products.
  4. There is no upper limit to the mass of hydrogen that can be exploded in a nuclear fusion process, so very large energies can be obtained. Nuclear fusion has been used in the hydrogen bomb.

Nuclear Fission

As was first shown in 1934 by Enrico Fermi, the heavy nucleus of Uranium-235 can be split into two other elements, Krypton and Barium, by bombarding it with a slow neutron

10n + 23592U → 14156Ba + 9236Kr + 310n + Energy

It was found that the total mass of the component products is less than the mass of the original Uranium. The difference in mass (mass defect) is a measure of the nuclear energy released. According to Albert Einstein

E = ∆mc2

where E is the energy released, ∆m is the difference in mass and c is the velocity of light. The amount of energy released when 1 g of Uranium-235 undergoes fission is about 7.4 x 1010 J, a prodigious amount of energy. This energy released in the form of heat.

Nuclear Fission is the splitting up of the nucleus of a heavy element into two approximate equal parts with the release of a huge amount of energy and neutrons.

Fission can occur with most of the very massive nuclei (e.g. Plutonium and Uranium) and has been produced by slow neutron, high-energy alpha particles, protons, X-rays and gamma-rays.

In the bombardment of Uranium-235 by slow neutron, several neutrons are produced as by-products. These neutrons may cause the splitting of other Uranium nuclei which, in turn yield more neutrons which may further split other Uranium nuclei and so on. Thus a chain reaction is set in motion. A chain reaction is a multiplying and self-maintaining reaction. When the size of Uranium exceeds a certain critical mass, there is a rapid production of neutrons accompanied by a release of a tremendous amount of energy in a nuclear explosion. This is the principle of the atomic and nuclear fission bombs.

Fission is also the process used in the present day nuclear power stations.

Applications of Radioactivity

Radioactive substances find very much application in

(i) Agricultural and scientific research

(ii) Medical field and

(iii) Industrial field

Agricultural and scientific research

Radioactive elements are used in agriculture as radioactive tracers and to induce mutations in plants and animals to obtain new and improved varieties. Biologists used them as tracers or markers to help trace the paths of metabolic processes in plants and animals. Geologists and archaeologists use the measurement of half-life to estimate the age or rocks, and carbon-14 (radiocarbon) to date recent organic remains. This is called radioactive dating.

Medical Field

Gamma-rays from radioactive substances are used to treat cancer patients, to sterilize surgical equipment, foods etc.

In Industry

Radioactive elements are used in industry (a) to study the defects in metals and welded joints, and to check metal fatigue. (b) As radioisotopes, they are used to trace underground pipe leakages.

Radioactive Hazard and Safety Precautions

Radioactive substances emit continuously powerful radiations such as β particles, ϒ particles and α particles ray. These are high energy radiation and hence, harm to living tissues. Energy absorbed by the passage of radiation through human body gives rise to the structural change called radiation damage. This damage may lead to death of a person. M. curie and E. Fermi lost their lives because of the damage caused by these radiations. When radiations enter a living system, the cell and tissues gets damaged due to the interaction with radiations. The harmful effects on an organism caused by these radiations is called radiation hazard. The damaged cell and tissue hamper normal functioning of the living system living ultimately to the death of the organism.

Following types of the damages can be caused by the radiation hazards:

  1. The exposure to radiation induces deleterious (harmful often in a subtle or an unexpected way ) genetic effects. When the radiation passes through genetic cells, there occur mutations of the chromosome of the cellular nuclei. The mutations are transmitted from one generation to the next and so on. The genetic effects are irreversible.
  2. The strong α-ray exposure can cause lung cancer.
  3. The exposure to fast and slow neutron can cause blindness.
  4. The exposure to neutrons, protons, and α particle can cause damage to red blood cells.
  5. The strong exposures to protons and neutrons can cause serious damage to reproductive organs.

Following are the safety precautions for radiation hazards.

  1. The radio isotopes should be transferred in thick wall lead containers and kept it rooms with thick walls of lead.
  2. The radio isotopes are handled with the help of remote control device.
  3. The workers are asked to wear lead aprons.
  4. The radioactive contamination of the working area is avoided at all casts.
  5. Nuclear explosions should be carried out far away from the public area.

Binding Energy

Nucleons are protons and neutrons in the nucleus of an atom. Binding energy is the energy required to take all the nucleons apart so that they are totally separated. When separated, it follows that the total mass is often less than the mass of the nucleus. Binding energy can also be referred t as the difference in mass.

Binding Energy = mass difference of nucleus and nucleons.

Questions

  1. Which of these is not relevant in the applications of radioactivity?
  2. Agricultural and scientific research B. Medical field C. Industrial field D. Carpentry field
  3. What are Beta particles?
  4. Protons B. neutrons C. electrons D. Helium nuclei
  5. The phenomenon of radioactivity was first discovered by
  6. Marie Curie B. Henri Becquerel C. Sir J. J. Thomson D. Enrico Fermi
  7. Alpha particles are
  8. not charged B. Highly penetrating C. electromagnetic radiation D. Helium nuclei
  9. Gamma radiation (γ) is a form of light, emitted as photons of energy hf, and has
  10. zero mass number and zero charge B. zero mass only C. zero charge only D. none is correct.

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