Nuclear Chemistry and Radioactivity – NDA Chemistry PYQs

Coastal States, Gulfs, Straits, Islands and Maritime Zones of India

Indian Geography • Coastal Geography • PYQs Included

Q1. NDA 2009-I
Which one among the following is used as a moderator in nuclear reactors?
(a) Ozone (b) Heavy hydrogen (c) Heavy water (d) Hydrogen peroxide
Answer: (c) Heavy water
Heavy water (D₂O, deuterium oxide) is used as a moderator in nuclear reactors. The moderator slows down fast neutrons released during fission to thermal (slow) neutrons. Slow neutrons are much more effective at causing further fission of uranium-235. Heavy hydrogen (deuterium) alone is not the same as heavy water.

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