From the following equations,pick out the possible nuclear reactions.

In a nuclear reactor, the main purpose of the moderator is to

In a nuclear reactor,heavy nuclei are not used as moderators because:

For nuclei with mass number close to $119$ and $238$, the binding energies per nucleon are approximately $7.6 \text{ MeV}$ and $8.6 \text{ MeV}$ respectively. If a nucleus of mass number $238$ breaks into two nuclei of nearly equal masses, what will be the approximate amount of energy released in the process of fission (in $\text{ MeV}$)?

$A$ ${ }_{92} U^{235}$ nucleus absorbs a neutron and disintegrates into ${ }_{54} X e^{139}$,${ }_{38} S r^{94}$,and $X$. What will be the product $X$?

In a fission reaction ${}_{92}^{236}U \to {}^{117}X + {}^{117}Y + n + n$,the binding energy per nucleon of $X$ and $Y$ is $8.5\,MeV$,whereas that of ${}^{236}U$ is $7.6\,MeV$. The total energy liberated will be about: