The function of heavy water in a nuclear reactor is to?

1. Slow down the speed of neutrons.
2. Increase the speed of neutrons.
3. Cooldown the reactor.
4. Stop the nuclear reaction.

Explanation

Option (a) is correct

• Heavy Water (D2O) or deuterium oxide is made up of two atoms of deuterium and one atom of oxygen. Deuterium is a stable isotope of hydrogen with double the mass of hydrogen due to presence of an extra neutron in its nucleus.
• Deuterium is present in hydrogen and hydrogen bearing compounds like water, hydrocarbons, etc. and has a small natural occurrence (D/D+H) of about 140 to 160 ppm. The same is extracted and enriched to > 99.85 mass % IP used in Pressurized Heavy Water Reactor (PHWRs).
• Heavy Water displays similar physical and chemical properties but differs in nuclear properties when compared to ordinary water which makes it an extremely efficient material for use as moderator and coolant in Pressurized Heavy Water Reactor (PHWRs).
  • Moderator is required in a nuclear reactor to slow down the neutrons produced during the fission reaction so that the chain reaction can be sustained. Heavy Water is an excellent moderator due to its high moderating ratio and low absorption cross section for neutrons.

Answer: (a) Slow down the speed of neutrons | Difficulty Level: Easy