In a nuclear fusion process,if the masses of the reactant nuclei are $m_1$ and $m_2$,and the mass of the resulting nucleus is $m_3$,then which of the following is true?

Fast neutrons can be easily slowed down by:

$A$ $1000 \; MW$ fission reactor consumes half of its fuel in $5.00 \; y$. How much $_{92}^{235} U$ (in $kg$) did it contain initially? Assume that the reactor operates $80 \%$ of the time, that all the energy generated arises from the fission of $_{92}^{235} U$, and that this nuclide is consumed only by the fission process.

Consider the fission of $_{92}^{238} U$ by fast neutrons. In one fission event,no neutrons are emitted and the final end products,after the beta decay of the primary fragments,are $_{58}^{140} Ce$ and $_{44}^{99} Ru$. Calculate the $Q$-value for this fission process. The relevant atomic and particle masses are:
$m(_{92}^{238} U) = 238.05079 \; u$
$m(_{58}^{140} Ce) = 139.90543 \; u$
$m(_{44}^{99} Ru) = 98.90594 \; u$
$m(_{0}^{1} n) = 1.008665 \; u$

In a nuclear fission process,a high mass nuclide $(A \approx 236)$ with binding energy $7.6 \ MeV/\text{nucleon}$ dissociates into two middle mass nuclides $(A \approx 118)$,each having a binding energy of $8.6 \ MeV/\text{nucleon}$. The energy released in the process is $MeV$.

The decrease in the mass of Uranium in a nuclear reactor operating at a power of $12 \text{ MW}$ per day is (Energy released in one ${}_{92}U^{235}$ fission is about $200 \text{ MeV}$):