UPSC CSE Prelims
Question 1
The function of heavy water in a nuclear reactor is to
View correct answer and explanation
Correct answer: A
Correct Option: A
Explanation: Heavy water (D₂O) is used as a neutron moderator in certain reactors. By reducing the speed of fast neutrons with relatively low neutron absorption, it helps sustain controlled fission.
Option-wise Analysis:
A: Correct - moderation slows neutrons so they can more readily cause fission in suitable fuels.
B: Incorrect - A moderator does not accelerate neutrons.
C: Incorrect - Water may also serve cooling functions in some reactor designs, but the asked principal heavy-water function is moderation.
D: Incorrect - Control rods, rather than heavy water, absorb neutrons to stop a chain reaction.