Which of the following is used as a moderator in nuclear reactors ?
A.
Plutonium
B.
Cadmium
C.
Heavy water
D.
Uranium
Answer :
Heavy water
Solution :
Moderator in a nuclear reactor is used to slow down the fast moving neutrons. Heavy water, graphite or beryllium oxide are used as moderators. Heavy water is best moderator. NOTE
In an ordinary uranium reactor, plutonium $$\left( {P{u^{239}}} \right)$$ is produced which is a better fissionable material than uranium $$\left( {{U^{235}}} \right).$$ It is a heavy isotope of uranium.
Releted MCQ Question on Modern Physics >> Atoms or Nuclear Fission and Fusion
In the nuclear fusion reaction
$$_1^2H + _1^3H \to _2^4He + n$$
given that the repulsive potential energy between the two
nuclei is $$ \sim 7.7 \times {10^{ - 14}}J,$$ the temperature at which the gases must be heated to initiate the reaction is nearly
[Boltzmann’s Constant $$k = 1.38 \times {10^{ - 23}}J/K$$ ]
The binding energy per nucleon of deuteron $$\left( {_1^2H} \right)$$ and helium nucleus $$\left( {_2^4He} \right)$$ is $$1.1\,MeV$$ and $$7\,MeV$$ respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is