Question

Why is heavy water used in nuclear reactors?

Answer 1

Hint :The heavy water has the same formula as that of water but the hydrogen atoms are replaced by an isotope of them. The heavier nuclei makes it useful for controlling the type of reactions that take place inside the nuclear reactors.

Complete Step By Step Answer:
Heavy water \[{D_2}O\] is the same as water molecule but with hydrogen atoms replaced by deuterium atoms i.e. one molecule of heavy water consists of two deuterium atoms bonded to one oxygen atom.
Nuclear reactors are the spaces where nuclear fission reactions are carried out. The reaction involves targeting a heavy and unstable nucleus (containing an excess of inter-nuclear particles) with a neutron that results in the splitting of the nuclei into lighter and smaller (also more stable than the heavy nuclei) nuclei. The fission reaction releases drastic amounts of heat in the process.
The high amounts of energy released as heat in nuclear reactors is channelized in making steam that is further used for electricity generation through turbines.
The heavy elements that are used in nuclear fission reactions are known as nuclear fuels. The most commonly used nuclear fuel is uranium.
The enormous amount of heat produced by these reactions needs to be controlled, only then it can be used for constructive purposes. Here comes the role of heavy water. It acts as coolant and moderator that keeps the heat in control. Not only does it absorb heat but also control the high speed neutrons involved in the fission reactions.
Though the heavy water is chemically not very distinct from normal water, it has enhanced nuclear properties due to which it acts as a coolant as well as moderator in nuclear reactors.

Note :
Deuterium is an isotope of hydrogen atoms which is quite stable. Being heavier than hydrogen (having double the number of neutrons as compared to hydrogen) it is more suited for nuclear reactions even though it contains the same number of protons and electrons.