Question

Which of the following substances is not used as coolant in nuclear reactors?

• A. Graphite
• B. Liquid sodium
• C. \( CO_2 \)
• D. Heavy water

Hint:

Graphite is a neutron moderator, not a coolant in nuclear reactors. Common coolants include liquid sodium, carbon dioxide, and heavy water.

Answer 1

The Correct Option is A

In nuclear reactors, coolants play a crucial role in removing heat generated from nuclear fission and maintaining reactor stability. Step 1: Understanding Nuclear Reactor Coolants - Common coolants used in nuclear reactors include: - Liquid sodium (used in fast breeder reactors). - Carbon dioxide (\( CO_2 \)) (used in gas-cooled reactors). - Heavy water (\( D_2O \)) (used in pressurized heavy water reactors).

Step 2: Evaluating the Options - Option (A) - Correct: Graphite is not a coolant, but it is commonly used as a moderator to slow down neutrons in reactors. - Option (B) - Incorrect: Liquid sodium is an effective coolant, especially in fast breeder reactors. - Option (C) - Incorrect: Carbon dioxide is used as a gas coolant in certain reactor designs. - Option (D) - Incorrect: Heavy water is a coolant in CANDU reactors.

Step 3: Conclusion Since graphite is primarily used as a moderator, not a coolant, the correct answer is option (A).