The energy liberated per nuclear fission is 200 MeV. If ${10}^{20}$ fissions occur per second the amount of power produced will be :

$\begin{array}{l}\mathrm{P}=\frac{{\mathrm{E}}_{\mathrm{tot}}}{\mathrm{t}}=\frac{{10}^{20}\times 200\mathrm{MeV}}{1}=2\times {10}^{22}\mathrm{MeV}/\mathrm{S}\\ =2\times {10}^{22}\times {10}^6\times 1.6\times {10}^{-19}\mathrm{J}/\mathrm{S}\\ =32\times {10}^8\mathrm{W}\end{array}$