The power obtained in a reactor using $^{235}U$ disintegration is $1000 \text{ kW}$. The mass decay of $^{235}U$ per hour is ............ $\mu g$.

For the following two nuclear reactions,the atomic number and mass number of nuclei $X$ and $Y$ are respectively:
$(I) \, _{92}^{235}U + _{0}^{1}n \rightarrow X + _{35}^{85}Br + 3 _{0}^{1}n$
$(II) \, _{3}^{6}Li + _{1}^{2}H \rightarrow Y + _{2}^{4}He$

The energy released per fission of uranium-$235$ is about $200 \, MeV$. $A$ reactor using $U-235$ as fuel is producing $1000 \, kW$ power. The number of $U-235$ nuclei undergoing fission per second is approximately:

The average energy of a neutron produced in the fission of ${ }_{92}^{235} U$ is

The physics behind a fusion test reactor is:

Heavy water is used as a moderator in a nuclear reactor because