Question

Fast neutrons can easily be solved down by

• A. the use of lead shielding
• B. passing them through water
• C. elastic collision with heavy nuclei
• D. applying a strong electric field

Answer 1

Answer: (B)

passing them through water

Answer 2

A neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction.
Commonly used moderators include regular (light) water (roughly $75 \%$ of the world's reactors), solid graphite ( $20 \%$ of reactors) and heavy water.