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  4. In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderators used have light nuclei. Heavy nuclei will not solve the purpose because

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Q. In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderators used have light nuclei. Heavy nuclei will not solve the purpose because

NTA AbhyasNTA Abhyas 2020

Solution:

During elastic collision between two particles, the maximum kinetic energy is transferred from one particle to the other when they have the same mass. Consequently, a neutron loses all its kinetic energy when it collides head on with a proton. For this reason materials which are abundant in hydrogen such as paraffin and water, are good moderates for neutrons.