Name: Nuclear Chain Reaction
Uploaded: 2019-07-19
Duration: 8 min 15 s
Description: Have you ever made a row of dominoes fall by pushing the first one? It is like a chain reaction. Learn about another type of chain reaction that happens on t...

Question

What is meant by nuclear fission? The fission process itself is not a chain reaction, why? Explain what step is taken to obtain chain reaction.

Accepted Answer

In the process of nuclear fission, a heavy nucleus like that of uranium breaks into two lighter nuclei. It occurs when the heavy nucleus is bombarded by other nuclear particles such as neutron. It is not a chain reaction itself but, the extra neutrons produced in this process can initiate the fission process again still producing more neutrons. Hence, there is a possibility of a chain reaction. The average energy of neutrons produced is about $2 MeV$ . Hence, their speed is very high. These neutrons will escape unless slowed down. For this, the elastic scattering of neutrons with the particles of almost the same mass is required. We know that in elastic scattering between the two particles of the same masses, velocities are exchanged. Hence, the neutron almost comes to rest and the deuterium nuclei carry the energy. Therefore, moderators with light nuclei such as heavy water are used to obtain a chain reaction of nuclear fission. Further, to make it a controlled chain reaction, the extra neutrons are to be absorbed by control rods. Cadmium is used for this purpose. These steps are followed in a nuclear reactor to get a controlled chain reaction.

What is meant by nuclear fission? The fission process itself is not a chain reaction, why? Explain what step is taken to obtain chain reaction.

Important Questions on Nuclear Fission and Nuclear Fusion : Sources of Energy

Learn and Prepare for any exam you want !