Question

Which of the following is used as a moderator in nuclear reactors?

• A. Plutonium
• B. Cadmium
• C. Heavy water
• D. Uranium

Answer 1

Answer: (C)

Moderator in a nuclear reactor is used to slow down the neutrons because slowing neutrons can easily make fission in $U^{235}$ or $P{u}^{239}$ . Heavy water, graphite or berillium oxide are used as modertors. Heavy water is best moderator. NOTE: In a ordinary uranium reactor, plutonium $(P{u}^{239})$ is produced which is a best fissionable material than uranium $(U^{235})$ . It is a heavy isotope of uranium.