OAS Mains-2019 Daily Answer Writing-11/05/2020

Paper:   General Studies Paper-II

Section:  Developments in the Field of Science and Technology, Communication and Space

Topic:  Science and Technology

Question 1

What is a fast breeder reactor? Discuss its role in India’s nuclear energy programme.

Sample Answer

Fast breeder reactor(FBR) is based on the design of the Rapsodie reactor of France. In this, the nuclear chain reaction is sustained by fast neutrons. When fission is induced by fast neutrons, the number of neutrons released per fission is more compared to that in thermal reactor. The extra neutrons are available for absorption in Uranium-238 to transform it to fissile Plutonium-239.

In the Production of electricity, though the operation of fast breeder reactor, the total energy potential in natural uranium can be better enhanced. The FBR is utilized for carrying out irradiation experiments to develop the fuel cycle of the fast reactors.

Role in India’s nuclear energy programme

FBR is of special importance for India because this country has immense supplies of thorium, which by itself can’t be used as fuel in N-reactors. On the other hand, India’s uranium reserves are limited. Since in these reactors, neutrons are not slowed down; they need special heat removal system such as liquid sodium or steam coolants in view of their higher power density.India has to depend on fast reactors for the first charge of U-233.

The thorium U-233 fuel cycle is of importance to India because of its nuclear fuel resource base.

Question 2

What are biofertilizers? What advantages do they have over chemical fertilizers?

Sample Answer

Biofertilizers are the culture of microorganisms such as rhizobium, azobacter, clastridium and blue algae as Nitrogen fixers, bacillus subtiles and micrortigal fungi as phosphate solubizers; azola as organic matter contributor and nitrogen fixer and throbacilles as sulphate producer; are used in supplementing the nutrient requirement of crops.

Instead of increasing the use of fertilizers, it is being increasingly realised that the same function could be achieved by improving and transferring Nitrogen fixation ability in plants


Biofertilizers have the advantages that they are renewable and non-pollutant. These are not alternative to chemical fertilizers but can play a supplementary role in supplying Nitrogen to specific crops under specific soil conditions.

Recently two biofertilizers namely, Rhizobium cultures and blue green algae have gained popularity amongst the farmers cultivating pulses/legume oilseeds and wet land rice respectively.

Biofertilizers have a limited role in augmenting the Nitrogen requirements of various crops.

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