What do you understand by controlled and uncontrolled chain react… - Vidyadip

Question

What do you understand by controlled and uncontrolled chain reactions?

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Answer

Controlled chain reaction : If the chain reaction of fission can be controlled in such a way that it neither increases nor decreases, that is, such a level of reaction is maintained such that the energy released per second always remains less than the limit of explosion. This is called controlled chain reaction. This type of reaction is used in the production of electrical energy. Controlled chain reaction is the fundamental basis of 'nuclear reactor'.
Uncontrolled chain reaction : In this reaction, on average, more than one neutron takes part in the process of fission out of the neutrons obtained from each fission. Here $K >1$. Due to this, the rate of fission of nuclei increases rapidly and within a few moments tremendous energy is released and causes a massive explosion. This reaction takes place in the atomic bomb.

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