Why is heavy water employed as a moderator

Question

Describe why is heavy water employed as a moderator? Illustrate.

Answer 1

Heavy water is highly enriched in the hydrogen isotope deuterium. We can evaluate the neutron interactions with billiard ball collision, where the neutron collides with nucleus of other atoms and lose energy. When the colliding nucleus size is small such as hydrogen nucleus it will lose the maximum energy. When nucleus is heavy, then the neutron hits the nucleus just alters its direction however not that much change in the energy of neutron. Therefore we use heavy water as moderator to slow down the neutrons.