Q. Which of the following can be used as coolant in nuclear reactors?
  1. Liquid sodium
  2. Helium (He) gas
  3. Water (H2O)
  4. Heavy water (D2O)
Select the correct option from the codes given below:

Answer: 1, 2, 3 & 4
Notes: All of the above can be used as coolant in nuclear reactor. Recently, Unit 1 of the Kakrapar Atomic Power Station was shut down after the leakage of heavy water that is used in cooling off the nuclear reactor core.