Question

It is absolutely necessary to control the fission reaction in nuclear power plants. Why?

Answer 1

Nuclear fission reaction in which the incident neutron is bombarded to the heavy target nucleus which is excited to a high energy level and then the nucleus splits into two fragments that results in the liberation of high amount of energy in the form of the radiation.

Nuclear power plants are established at the same principle However, the crucial thing is that, the fission process produce $2,3$ or more free neutrons that are capable of inducing further fission and so on.

This results in a chain reaction, and initially controlled This leads to further fission, further generation of neutrons, and continuous increase in amount of energy liberated.

If not controlled then this exponential increase in energy can be very dangerous, this concept is harnessed in production of nuclear bombs. In a nuclear reactor, this may lead to a blast, releasing harmful radiations that may be fatal or cause long lasting damage to organisms and environment.

Thus, it is absolutely necessary to control the fission reaction in nuclear power plants.

And to control the chain reaction, control rods are used which are simply sheets of element Cadmium, an excellent neutron absorber