Question

Which one of the following cannot be used as a moderator in a nuclear reactor?

• A. Water
• B. Heavy water
• C. Molten sodium
• D. Graphite

Answer 1

Answer: (A)

Water

Answer 2

Moderator is used to slow down the fast moving neutrons.Most commonly used moderator, are graphite and heavy water $(D_2 O)$.Water cannot be used as moderator in a nuclear reactor.