(A) : Heavy water is used as moderator in nuclear reactors.
(B) : Heavy water undergoes exchange reaction in nuclear reactor.
Heavy water is used as moderator in nuclear reactors to control the speed of neutron.
→ Heavy water is used in the Exchange reactions to study of reaction mechanism.
Ex: Isotopic effect
Isotopic effect is used to study the rate of reaction
→ Heavy water donot undergoes exchange recation in nuclear reactor.