$A$ nuclear reactor process is said to be critical when the value of the multiplication factor is .......

$A$ $\pi^0$ meson at rest decays into $2$ $\gamma$ rays: $\pi^0 \to \gamma + \gamma$. Which of the following must happen?

To generate a power of $3.2 \text{ MW}$,the number of fissions of $^{235}\text{U}$ per minute is (Energy released per fission $= 200 \text{ MeV}$,$1 \text{ eV} = 1.6 \times 10^{-19} \text{ J}$)

$A$ $^{235}U$ nuclear reactor generates energy at a rate of $3.70 \times 10^7 \text{ J/s}$. Each fission liberates $185 \text{ MeV}$ of useful energy. If the reactor has to operate for $144 \times 10^4 \text{ s}$, the mass of the fuel needed is (Assume Avogadro's number $= 6 \times 10^{23} \text{ mol}^{-1}$, $1 \text{ eV} = 1.6 \times 10^{-19} \text{ J}$) (in $\text{ kg}$)

The energy released in a typical nuclear fusion reaction is approximately..........$MeV$.

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).