Neutron moderation is the process of slowing down fast-moving neutrons produced during nuclear fission to thermal (low) energies, where they are more likely to cause further fission in certain fuel types like uranium-235.
Why It Matters:
- In thermal reactors, slow (thermal) neutrons are much more effective at inducing fission in fuel nuclei.
- Fast neutrons are less likely to interact with fissile material unless slowed down.
How It’s Done:
- A moderator is used—typically a substance with light nuclei that effectively slows neutrons through elastic collisions.
- Common moderators include:
- Water (ordinary or heavy water)
- Graphite
- Beryllium
Effect on Reactor Operation:
- Moderation increases the likelihood of sustaining a chain reaction.
- Helps maintain reactor efficiency and stability.
In summary, neutron moderation is essential in thermal reactors because it enhances the ability of neutrons to cause further fissions, thereby ensuring a steady and controlled release of energy.