Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because

What is used as a moderator in a nuclear reactor?

The binding energy of deuteron is $2.2 \, MeV$ and that of $_2^4He$ is $28 \, MeV$. If two deuterons are fused to form one $_2^4He$,then the energy released is ......... $MeV$.

Consider the nuclear fission reaction ${ }_0^1 n+{ }_{92}^{235} U \longrightarrow{ }_{56}^{144} Ba+{ }_{36}^{89} Kr+3{ }_0^1 n$. Assuming all the kinetic energy is carried away by the fast neutrons only and total binding energies of ${ }_{92}^{235} U, { }_{56}^{144} Ba$ and ${ }_{36}^{89} Kr$ to be $1800 \ MeV, 1200 \ MeV$ and $780 \ MeV$ respectively,the average kinetic energy carried by each fast neutron is (in $MeV$):

Fusion reaction takes place at high temperature because

$A$ star initially has $10^{40}$ deuterons. It produces energy via the processes:
$_1H^2 + _1H^2 \to _1H^3 + p$
$_1H^2 + _1H^3 \to _2He^4 + n$
The masses of the nuclei are as follows:
$M(H^2) = 2.014 \, amu; \, M(p) = 1.007 \, amu;$
$M(n) = 1.008 \, amu; \, M(He^4) = 4.001 \, amu$
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: