Nuclear Fusion

Question 1 What is nuclear fusion reaction? Write the equation of the reaction involved?

Question 2 Why are very high temperature required for fusion to occur?

Question 3 What is the nuclear fuel in the sun? Describe the process by which energy is released in the sun?

Question 4 What is the source of energy of the sun and other stars?

Question 5 Describe the working of hydrogen bomb?

Question 6 What are the advantages of nuclear energy?

Question 7 What are the disadvantages of nuclear energy?

Question 8 What are the various factors which we keep in mind while choosing a source of energy?

Question 9 What are the environmental consequences of the increasing demand for energy?

Question 10 What steps would you suggest to reduce energy consumption?

Nuclear Fusion

The process in which two nuclei of light elements (like that of hydrogen) combine to form a heavy nucleus (like that of helium), is called nuclear fusion.

 

A tremendous amount of energy is produced during the fusion process.

When two nuclei are brought together, they repel each other due to their similar charges. Due to this a lot of initial heat energy and high pressure are required to force the lighter nuclei to fuse together to form a bigger nucleus. So, the conditions needed for carrying out nuclear fusion process are ‘millions of degrees of temperature’ and ‘millions of pascals of pressure.

There is some loss of mass during the fusion process which appears as a tremendous amount of energy.

When deuterium atoms are heated to an extremely high temperature under extremely high pressure, then two deuterium nuclei combine together to form a heavy nucleus of helium, and a neutron is emitted. A tremendous amount of energy is liberated in this fusion reaction.

This fusion reaction can be written as:

The energy produced in nuclear fusion reaction is, however, much more than that produced in a nuclear fission reaction. Nuclear fusion energy could not be used for generating electricity so far.

The nuclear reactions which occur at extremely high temperatures are called thermonuclear reactions. 

Hydrogen bomb

The hydrogen bomb consists of heavy isotopes of hydrogen called deuterium and tritium along with an element lithium-6. When the atom bomb is exploded, then its fission reaction produces a lot of heat. This heat raises the temperature of deuterium and tritium to 10⁷ °C in a few microseconds.

At this temperature, fusion reactions of deuterium and tritium take place producing a tremendous amount of energy. This explodes the hydrogen bomb releasing an enormous amount of energy in a very short time.

The function of lithium-6 used in hydrogen bomb is to produce more tritium needed for fusion. This is because when lithium is hit by neutrons (produced during fusion reactions), it forms tritium and helium.

A hydrogen bomb is based on the thermonuclear fusion reactions of heavy hydrogen atoms (like deuterium and tritium) to produce helium atoms. The hydrogen bomb (based on nuclear fusion) is exploded by using an atom bomb (based on nuclear fission). A hydrogen bomb is actually an uncontrolled nuclear fusion process. The source of energy of a hydrogen bomb is the same as that of the Sun’s energy, the only difference being that sun’s energy supports life on earth, whereas the energy of hydrogen bomb destroys life on earth.

 

The Source of Sun’s Energy

The sun is a big thermonuclear furnace where hydrogen atoms are continuously being fused into helium atoms. Mass is being lost during these fusion reactions and energy is being produced. Thus, the sun which gives us heat and light, derives its energy from the fusion of hydrogen nuclei into helium nuclei, which is going on inside it, all the time.

The main nuclear fusion reaction taking place in the sun which releases a tremendous amount of energy is the fusion of 4 hydrogen atom nuclei to form a bigger nucleus of helium atom. 

The total energy produced by the fusion of hydrogen into helium is tremendous. All this energy is released in the form of heat and light. It is this energy which makes the sun shine and give us heat and light. Thus, nuclear fusion reactions of hydrogen are the source of sun’s energy. Stars also obtain their energy from the nuclear fusion reactions of hydrogen.

Advantages of Nuclear Energy

(1) It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).

(2) Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.

(3) It does not produce gases like carbon dioxide which contribute to greenhouse effect or sulphur dioxide which causes acid rain.

Disadvantages of Nuclear Energy

(1) The waste products of nuclear fission reactions (produced at nuclear power plants) are radioactive which keep on emitting harmful nuclear radiations for thousands of years. So, it is very difficult to store or dispose of nuclear wastes safely. Improper nuclear waste storage or disposal can pollute the environment.

(2) There is the risk of accidents in nuclear reactors (especially the old nuclear reactors). Such accidents lead to the leakage of radioactive materials which can cause serious damage to the plants, animals (including human beings) and the environment.

(3) the high cost of installation of nuclear power plants and the limited availability of uranium fuel make the large scale use of nuclear energy prohibitive.

 

Environmental consequences of the Increasing demand for energy

(1) The combustion of fossil fuels is producing acid rain and damaging plants (crops), soil and aquatic life.

(2) The burning of fossil fuels is increasing the amount of greenhouse gas carbon dioxide in the atmosphere.

(3)The cutting down of trees from the forest (deforestation) for obtaining fire-wood is causing soil erosion and destroying wild life.

(4) The construction of hydro-power plants is disturbing ecological balance

(5) Nuclear power plants are increasing radioactivity in the environment.

The various factors which we should keep in mind while choosing a source of energy are:

(i) the ease of extracting energy from that source

(ii) the cost of extracting energy from the source

(iii) technology available to extract energy from that source, and

(iv) the damage to environment which will be caused by using that source.

How Long Will Energy Resources of Earth Last

Most of the energy that we use today comes mainly from the three non-renewable energy resources of the earth : coal, petroleum and natural gas (which are called fossil fuels). We have been using these resources of the earth at a very rapid rate in the past. So, the amount of coal, petroleum and natural gas left in the earth is limited. It is high time that we start using alternative sources of energy to conserve the depleting reserves of coal, petroleum and natural gas so that they may last longer.

Steps which can be taken to reduce energy consumption are :

(1) Switch off lights, fans, TV and other such electrical appliances when not needed, to save electricity.

(2) Use energy efficient electrical appliances to save electricity. This can be done by using compact fluorescent lamps (CFL) and tube-lights in place of conventional filament-type electric bulbs.

(3) Good quality stoves should be used to burn fuels like kerosene and LPG so as to obtain maximum heat.

(4) Pressure cookers should be used for cooking food to save fuel.

(5) Solar cookers should be used to cook food whenever possible and solar water heaters should be used to get hot water.

(6) The use of biogas as fuel should be encouraged in rural areas.

(7) Bicycles should be used for short distances to save precious fuel like petrol (which is used in cars, scooters and motorcycles).