Which of the following are suitable for the fusion process?

Fast neutrons can be easily slowed down by:

The minimum kinetic energy needed by an alpha particle to cause the nuclear reaction ${ }_{7}^{16} N +{ }_{2}^{4} He \rightarrow{ }_{1}^{1} H +{ }_{8}^{19} O$ in a laboratory frame is $n$ (in $MeV$). Assume that ${ }_{7}^{16} N$ is at rest in the laboratory frame. The masses of ${ }_{7}^{16} N, { }_{2}^{4} He, { }_{1}^{1} H$ and ${ }_{8}^{19} O$ can be taken to be $16.006 \ u, 4.003 \ u, 1.008 \ u$ and $19.003 \ u$,respectively,where $1 \ u = 930 \ MeV/c^2$. The value of $n$ is. . . . .

$1 \, g$ of hydrogen is converted into $0.993 \, g$ of helium in a thermonuclear reaction. The energy released is

Which of the following is the best neutron moderator compared to all others?

The fission of a $_{92}U^{235}$ nucleus releases $200 \, MeV$ of energy. Find the rate of fission of $_{92}U^{235}$ required to operate a reactor at a constant power of $5 \, W$.