The best neutron moderator is:

The thermonuclear reaction of hydrogen inside the stars takes place by a cycle of operations. The particular element which acts as a catalyst is

The average energy released per fission for the nucleus of $_{92}^{235} U$ is $190 \text{ MeV}$. When all the atoms of $47 \text{ g}$ pure $_{92}^{235} U$ undergo fission process,the energy released is $\alpha \times 10^{23} \text{ MeV}$. The value of $\alpha$ is . . . . . . . . . . . (Avogadro Number $= 6 \times 10^{23} \text{ per mole}$)

The source of the Sun's energy is

$A$ chain reaction is continuous due to

The mechanism of the hydrogen bomb is based on