In a nuclear reactor,boron rods are used as ...... .

$A$ star has $10^{40}$ deuterons. It produces energy via the processes:
$_1H^2 + _1H^2 \to _1H^3 + p$
$_1H^2 + _1H^3 \to _2He^4 + n$
If the average power radiated by the star is $10^{16} \ W$, the deuteron supply of the star is exhausted in a time of the order of:
Given:
Mass of $_1H^2 = 2.014 \ amu$
Mass of $_2He^4 = 4.001 \ amu$
Mass of proton = $1.007 \ amu$
Mass of neutron = $1.008 \ amu$

The average number of prompt neutrons produced per fission of ${U^{235}}$ is

In the proton-proton cycle in the Sun,the energy released when an electron and its antiparticle combine is $\qquad$ .

Statement $1$: Energy is released during the fission of heavy nuclei or the fusion of light nuclei.
Statement $2$: Binding energy per nucleon increases with an increase in $Z$ for heavy nuclei,whereas it decreases with an increase in $Z$ for light nuclei.

In an $\alpha -$ decay,the kinetic energy of the $\alpha -$ particle is $48 \ MeV$ and the $Q$ value of the reaction is $50 \ MeV$. The mass number of the mother nucleus is (assume that the daughter nucleus is in the ground state).