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:

In an atomic bomb,the energy is released due to

Which of the following nuclear fragments corresponding to nuclear fission between a neutron $\left({ }_{0}^{1} n\right)$ and a uranium isotope $\left({ }_{92}^{235} U\right)$ is correct?

When a slow neutron goes sufficiently close to a ${U^{235}}$ nucleus,then the process that takes place is

Suppose a ${ }_{88}^{226} Ra$ nucleus at rest and in the ground state undergoes $\alpha$-decay to a ${ }_{86}^{222} Rn$ nucleus in its excited state. The kinetic energy of the emitted $\alpha$ particle is found to be $4.44 \text{ MeV}$. The ${ }_{86}^{222} Rn$ nucleus then goes to its ground state by $\gamma$-decay. The energy of the emitted $\gamma$-photon is . . . . . . . $\text{keV}$.
[Given: atomic mass of ${ }_{88}^{226} Ra = 226.005 \text{ u}$,atomic mass of ${ }_{86}^{222} Rn = 222.000 \text{ u}$,atomic mass of $\alpha$ particle $= 4.000 \text{ u}$,$1 \text{ u} = 931 \text{ MeV}/c^2$]

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