$A$ chain reaction is continuous due to

In a nuclear reactor,heavy nuclei are not used as moderators because:

Explain an example in which heat transfer is necessary.

The nuclear reaction $^2H + ^2H \to ^4He$ (mass of deuteron $= 2.0141 \,amu$ and mass of $He = 4.0024 \,amu$) is

Pick out the unmatched pair from the following $:-$

Imagine that a reactor converts all given mass into energy and that it operates at a power level of $10^9\, W$. The mass of the fuel consumed per hour in the reactor will be: (velocity of light,$c = 3 \times 10^8\, m/s$)