Nuclear Fission

Otto Hahn and Strassman found that Uranium-235 bombarded by a neutron splits up into two comparatively lighter nuclei. This process is known as nuclear fission. The neutrons used in the fission of the Uranium nucleus have low energy and are known as thermal neutrons. During the fission of uranium, two or three neutrons are also emitted along with the release of a large amount of energy besides the products of the fission.

Thus, the process of splitting a heavy nucleus into two comparatively lighter nuclei along with the release of a large amount of energy when bombarded with a thermal neutron is called nuclear fission. 

Nuclear fission of ₉₂U²³⁵ when bombarded with a slow neutron (known as thermal neutron) is given below: 

₉₂U²³⁵ + ₀n¹ → ₅₆Ba¹⁴¹ + ₃₆Kr⁹²+ 3 ₀n¹ + Energy 

The energy released per fission of ₉₂U²³⁵ (an isotope of uranium) is about 200 MeV. This fission is represented in the figure below: 

Note: It may be noted that nuclear energy produced by the fission of 1 kg of uranium – 235 is equal to the energy produced by the burning of 25,00,000.

Pollution from Nuclear fission

Nuclear fission causes more serious pollution problems than fossil fuels. During nuclear fission, nuclear radiation namely alpha particles (u-particles), beta particles (B-particles) and gamma rays (y-rays) are emitted. This radiation is very harmful to living organisms. The long and constant exposure of living organisms to these radiations cause many diseases or disorder in the human body like: 

1. Nuclear radiation can change or damage the structure of cells in the human body
2. They cause diseases like cancer, leukemia, and blindness.
3. They cause genetic disorders in the human body.
4. They cause sterility in the young generation.

Advantages and Disadvantages of Nuclear fission

The advantages of using nuclear fission energy are:

• A small quantity of nuclear fuel (U-235) gives a large amount of energy by the process of nuclear fission while to produce a large amount of heat large quantity of fossil fuel is required. e.g. 1 kg of Uranium 235 releases energy equivalent to the energy released by the burning of 25,00,000 kg coal.
• In a nuclear power plant, the nuclear fuel is inserted once to get energy over a long period of time. On the other hand, in a thermal power plant, fossil fuel is to be supplied constantly to get the energy.

The disadvantages of using nuclear fission energy are:

• Nuclear fission causes more serious pollution problems than the burning of fossil fuels. During nuclear fission, radiation is emitted which is very harmful. They cause dangerous diseases like cancer, leukemia, and sterility.
• The biggest problem of using nuclear fission energy is the safe disposal of nuclear waste. Nuclear waste continues to emit harmful nuclear radiation. Their complete elimination of nuclear waste is impossible while fossil fuel waste can be completely eliminated. e.g. if we burn coal it will give rise to ash which can be thrown in the fields.

The nucleus of an atom is very small. But it is a matter of fact that a single tiny nucleus of an atom will produce a massive amount of nuclear energy? What is the source of this electricity, and how does this is obtained? Let’s take a closer look at nuclear technology and how it differs from other types of energy.

What is Nuclear Energy?

Nuclear energy is the energy stored within the nucleus of an atom, which is a small particle that makes up all matter in the universe. The mass of an atom is normally concentrated in the nucleus centre. The nucleus is composed of two subatomic particles: neutrons and protons. Bonds that hold atoms together provide a huge amount of energy.

Radioactivity

Antonie Henri Becquerel, a French physicist discovered that Uranium emits radiation spontaneously. The spontaneous emission of radiation by uranium or heat elements is known as radioactivity. A substance or element that shows the property of radioactivity is known as a radioactive substance or radioactive element.

In 1897, Rutherford found that the radiation emitted by radioactive elements are of three types:

(i) Alpha particle: The alpha particle is a helium nucleus i.e. a helium atom that has lost its two orbital electrons.

(ii) Beta particle: The Beta particles are the streams of fast-moving electrons. 

(iii) Gamma rays: The gamma rays are simply the radiation of small wavelengths. 

When a radioactive substance emits radiation, its mass decreases. Suppose M be the mass of a radioactive substance before emitting the radiation and M be the mass of the substance after emitting the radiation. Therefore, the decrease in the mass of the substance is given by:

△m = (M – M’) 

This decrease in mass (△m) is converted into energy E according to Einstein’s mass-energy relation, 

E = △mc²

where c the speed of light in a vacuum which is equal to 3 × 10⁸ m/s and the energy E is known as nuclear energy.

Unit of Nuclear Energy: Nuclear energy is expressed in Electron-volt (eV). 

Therefore, 1 eV is defined as the energy acquired by an election while passing through a potential difference of one volt. The nuclear energy of 1 eV is equivalent to Joules:

1 eV = 1.6 x 10^-19 C × 1 V = 1.6 × 10^-19 CV or 1.6 × 10^-19 J. 

Another unit for nuclear energy is Mega electron-volt (MeV). The nuclear energy of 1 MeV is defined as:

1 MeV = 10⁶ eV = 10⁶ × 1.6 × 10^-19 J = 1.6 × 10^-13 J.

Nuclear Reactions 

Atomic nuclei undergo modifications as a result of nuclear reactions, which result in changes in the atom itself. Nuclear reactions change one aspect into something entirely new. However, nuclear scattering happens as a nucleus interacts with other particles and then splits without changing the properties of the other nuclei.

There are two kinds of nuclear reactions that can produce nuclear energy:

(i) Nuclear Fission: Nuclear fission is the mechanism by which a radioactive atom’s heavy nucleus, such as plutonium or uranium, breaks into smaller nuclei when bombarded by low-energy neutrons.

(ii) Nuclear Fusion: The reaction which requires the fusion of two light elements to produce a heavier element and the release of energy is called the nuclear fusion.